I'm not a tranny guy and I don't play one on tv, but I did just finish disassembnling and repairing the tranny on my 84. That said, auto trannies are not the big hairy monsters I thought they were. I would suspect that you had some blocked passages in your valve body that were cleaned out by using the transx and lucas snake oils. Keep using the transx for a few changes to keep cleaning the passages. Ensure the bowden is adjusted properly, that the vacuum modulator is getting good vacuum and is capable of holding it. Adjust the modulator to make it shift right, be sure the alda line is clean. Then put in some good tranny fluid and give it a go. If it shifts good, and doesn't flare, you're probably fine.

If you want to replace it. See if your indy will do the swap for a couple hundred bucks and buy a rebuilt from Sun Valley in CA. 2 year warranty.

Good Luck.