The degree wheel and pressure tester are good ideas.
I don't use tools (except a HF Heat Gun) to assemble the cases.
I put the side of the case with the threads on 2 pieces of 2 X 4 (for clearance), heat the bearing, and the crank drops right in. Wear gloves, don't burn yourself! Make sure the rod is "up" so the crank fits into the case.
Make sure your case pins are in tight (this has been a problem) as they can cause great damage if they move after the saw is done (especially the one that goes into the clutch area).
I then heat the other bearing (be careful, that one usually has a nylon race that can not be over heated) and start it down the crank and align with the case pins. (Don't forget the gasket, I leave them dry) It usually does not go all the way down for me, but goes down enough for me to start the case bolts.
Get a 6" long T-27 bit and put it in a cordless drill to make things go faster. Also get a T handle T-27 if you don't already have one. I do a "torque pattern" on the bolts on setting "5", then tap the case with a hammer, then repeat on setting "10", repeat tapping, then "15" and keep going on 15 till it meets.
When you are finished, look to see if the crank is centered. Even if it looks centered you will want to tap it (moderate taps) in both directions with a steel hammer. This will center your crank and bearings and you will keep doing it until the crank spins freely (the seals will always provide some resistance).
Speaking of, don't forget to coat the seals with Vaseline or grease, and I always purchase extra seals (in advance) in case you ruin one (it is always the one on the second portion of the case, be careful when it goes over the lip of the crank.
Best of luck with it, hope this information helps you. I've done about a dozen cases this way w/o any problems, save two bad seals! (The seals are pre installed, you can leave them in).
Clean all bearings and lube them with WD-40 before assembly. Also make sure the cases are clean. One of the biggest problems is they often ship things with grit in them. Check main bearings and crank bearings before assembly, they should be smooth and free of any play.