Adding a quick update to this thread...I've been in discussions with a member on FB who is rebuilding his transmission as I write this. I was able to dig out the custom tool I made to pull the large center bearing off the main shaft for transmission disassembly.
Note: that I lost the photos of this step in the process. Also note, that I made a similar tool for the input shaft bearing removal prior to realizing that I could remove the input shaft and bearing as a whole on an 88/89.
Here are the tools. I made these out of 4140 steel, which is pretty high strength. This may have been overkill. I also wrapping them around the bearing as much as I could to limit flange deformation....again, may have been overkill. The lip is only .050" thick in order to get between the underside of the bearing flange and the transmission case. As seen, I used some scrap hollow structural steel and tacked it to the tool halves once around the bearing....being that the material was 4140, it doesn't take kindly to welding and my tacks broke...which caused no issue. Thus disregard this feature, it isn't needed. The holes are drilled/tapped to 1/2-13 thru and I used ASTM A193 B7 all thread rod (which is basically 4140 steel too) as the extension to a standard puller bar.
Obviously, these were made on a lathe and mill. I had access to a local machine shop at the time who let me create these while on my lunch breaks at work at the time. Probably more elaborate than most would have done, but you can use the principle to design something similar. I use to have actual drawings of these but they were also lost with the photos. But they are easy to make...measure the diameter of the bearing flange and the bearing body with a .050" thick lip. The total thickness of these are 1/2". Definitely could try a much more crude tool made out of 1018 or A36 steel with 1/2-13 nuts welded to them in lieu of the tapped holes.
I don't have a tranny a part to show the setup on but thought I'd at least post pictures of the tool on one of my spare center bearings.
The member on FB ended up not using anything like this but rather setting up the transmission in a harbor freight shop press and pressed down on the main shaft...using the transmission case to resist the bearing as the shaft was pushed off of it. He has a nice little video of it on FB showing the process, which I'm trying to figure ou how to link here. He said he may put it up on youtube for the purpose....I'll update this if he does.