Part # a plus.
I have two to rebuild. and know I needs some special tools just for this unit.
Neither are for my cutlass, but I figured I'd ask here as their are some great minds here.
Thanks.

 

Nothing, really, as long as you have a method to compress the return springs in a drum. The ~$30 tool on amazon is actually quite good.

The low/reverse support tool, especially the metal one, makes dealing with that part easier but it's not strictly necessary and they have gotten very hard to find/ Removing the L/R is usually easy if the core isn't mangled - flip the unit upside down and whack it with a dead blow. Installing is the tricky part but I did it with some bent rebar wire the first couple of times. Pump alignment tools are just a big band clamp - buy a few of the largest band clamps at the local hardware store, wind them together, and you have a tool that's just as effective. Dial indicators and a variety of tips/mounts are also helpful but the checks can be done with feeler gauges and straight edges. Lip seal tools are nice but feeler gauges work just as well. It is easy to mangle bushings if you don't have the right size things to press them, but a good bushing press kit is all you need, not a specialty kit. Some of the other trans have some funky bushings - the th400/4l80e center support bushing is a good example - that are easier to do with a special tool but it's still not necessary. Air compressor is a must, and a blow gun with a soft tip lets you do air checks. The various snap rings can be annoying. I ended up with a wide variety of c-clip and snap ring pliers because some rings are just a bit too big, some are in a hole that's just a bit too small, some have just a tiny bit too little area to work, etc. This is my current favorite for snap rings:
The only thing I'd consider essential is an engine stand adapter so you can hang the trans from an engine stand and spin it around. I cobbled one together from some 2x2 steel tube and random bolts. Just need a bit bolt (preferably 7/16 or 1/2) coming in from each side to go into those little pockets and another coming down from the top to stop it from swiveling. Something like this, but I just put a plate on the back that bolted to the engine stand's engine adapter. I prefer to move it around instead of being bolted to the bench.
The only unique supply is transgel


There's several videos on youtube that show how to work on these with basic hand tools. The special tools are just a little faster/easier/fool-proof.

 

The CK Performance book tells you how to rebuild the 200-4R without the Kent-Moore tools, but frankly it is MUCH easier with them. I got all of mine on eBay and they are all still available today.