I have to say I'm digging the black wheels on this car. They work well with the black hardtop. I'm thinking a small ducktail spoiler on the back might work well now. These wheels weigh only 10.4 pounds so the car feels great. I don't know how much grip to expect from these tires, so I'll be taking it a little easy until I get a feel for them.
So now it was time to assemble everything. I started with the rods and pistons. These are fairly easy to assemble. I was wishing for a better set of snap-ring pliers but I managed to get them together. Assembly is made easier by either getting the wrist pin cold, or making the piston hot. I think the hot method is better because the cold method resulted in condensation forming on the pin, which made it slightly wet. I used plenty of assembly lube and gently tapped the pin into place, and then snapped-in the snap rings. MAKE SURE YOU INSTALL BOTH SNAP RINGS! I almost left one out which would have cost me the engine.
Once all the pistons were assembled to the rods, I moved on to the rings.
The rings are clearly labeled as to which rings they are, and also to which way is up. 
You have to space out the end-gaps so they don't line up. My shop manual spelled out exactly how to space them. This photo shows only the oil control rings assembled. Note that the spacer ring has an up-down direction, but the oil control rings don't.
The first and second compression rings are not identical and also have an up and a down. Don't mess this up! I used a pair of ring pliers to get the compression rings in place. They're quite stiff so it would be hard to get them on with your fingers. The oil control rings are easy and you won't need the pliers for them.
Do not buy this tool to compress your rings, or if you did, deposit it directly in the trash. I deposited two of them in the trash before I learned my lesson.
Meanwhile, I installed the main bearing top halves and gently laid the crank in place, then torqued down the bearing caps (with the bearing halves installed, of course, and plenty of assembly lube). Don't forget the thrust washers on the number 4 journal. The crank spins freely in the block at this point.
This is the hardest part of the build - getting the pistons in the bores. The cheap ring compressors flat didn't work so I bought a better tool, which worked but was still really hard to use. This photo shows three pistons in place. Took me about an hour to get to this point. The first oil control ring likes to sneak out from under the compressor and hang up on the rim of the cylinder just as you are tapping the piston in. Like, 90 percent of the time. Note that there is a front and back to the pistons. These DNJ pistons have a round mark on the top indicating the front of the engine. There is a cut-out area of the skirt to clear the oil squirter in the block. If you install the piston backwards it will collide with the squirter.
This is the tool that actually works. Mind you, the oil control ring still hangs up 9 times out of 10, but it eventually works and you don't get your hands all sliced up and your block scratched. I got this one on Amazon and it's a GearWrench brand tool. It comes in a nice case and has a variety of rings for many different bore sizes. I'll probably never use it again, but I have it.
I found that if it kept hanging up on the rim of the cylinder if I reoriented the tool on the piston sometimes it would go in. You have to be careful not to mess up the spacing of your ring gaps while wrestling with this. I probably did. I gently tapped each piston into place with a wooden handle. Once the oil control rings get past the rim, the whole thing goes in easier. If you feel increased resistance, STOP. If you force it you will bend a ring and score the cylinder wall. Keep everything coated and lubricated with oil while doing this. 
When you're tapping the pistons in, make sure to put some tape over the end of the rod bolts, so they won't scratch the crank journals. I fount it best to rotate the crank so each rod journal was at its lowest point before I installed the rod.
Finally I installed the rod bearing caps, again with plenty of assembly lube. With the pistons connected to the crank it doesn't spin quite as easily but you should still be able to move it by hand. If you can't, something is wrong.
I'm picking this project up sort of in the middle here, because I've already got the engine out and on a stand. When I last had the engine out in 2012, the cylinder bores looked very good, so I think I can get away with a simple hone and re-ring job, with new crank and rod bearings. I plan to use a Flex-Hone rotary brush type honing tool. These are inexpensive, can be done by hand with a drill, and provides a high-quality finish with the proper cross-hatch angle to ensure a good seal by the rings. I've torn down a spare 2002 engine block we had at the Gorilla Garage and I plan to use it to practice my honing technique. I also plan to use the pistons from that engine to take advantage of the 10:1 compression ratio enjoyed by the 2002 Miata engine. This will be a true budget-build, because if the block looks and measures ok, I'm going to get by without doing any machine work. We'll see if that pans out! The head only has maybe 35k miles on it, so I'm hoping to leave it alone at this time.
To sum up part 1 of this series, here are my goals for this project:
As usual with my blog, this is not a how-to. It's a you-can. There are plenty of forum posts and blog entries elsewhere that will tell you everything you need to know to complete this maintenance.
I started with an order of parts from ECS Tuning.
To start I removed the lower engine shield, fan with clutch, fan shroud, intake filter housing, hoses, belts, and finally the radiator. The lower radiator hose was impossible to get loose from the rad so I left it in place and removed both through the bottom of the car. You have to move the oil cooler out of the way but you can leave it attached. Support it with something so it's not hanging by the oil hoses.
When removing the thermostat housing there's a coolant pipe that runs between the housing and the bigger pipe that runs to the back of the engine. It's about 2 inches long and machined from aluminum. It is sealed with O-rings (#11537830709) on both ends. Mine pulled free from the engine end, not the thermostat housing end, and thus the whole housing was too big to remove from the space it occupies. I had to work for quite a few minutes to get the pipe loose from the housing side so I could remove it. Most write-ups I've seen don't tell you to remove that pipe at all, but there is an o-ring on the engine end that you should replace as well, so it's just as well that it came out that way.
Once the thermostat housing and thermostat are out of the way, you can unbolt the water pump. A firm pull disengages the pipes on the back side and it easily comes out.
At this point I assessed where I was and decided I needed a few more parts to do a more thorough job. Again from ECS, I ordered:
Once I had the hoses replaced, everything went back together quite quickly. Access to the cooling system on the M3 is very good and doesn't require many contortions (except for those three hoses under the intake manifold). While I was in there, I also replaced the main serpentine belt tensioner spring and pulley. I had bought them a long time ago so they are not listed in the parts list above. The bolts that hold the water pump to the block should be tightened to 7 lb-ft of torque. That is NOT VERY MUCH. I don't even have a torque wrench that will read that low. I used a 1/4-inch ratchet and very gently torqued these bolts down. The bolts that hold the pulley to the water pump snout are also torqued to 7 lb-ft. Be careful!
