No forward gears, harsh reverse

Hello guys, I've been lurking on this forum for about two weeks trying to learn as much as I could and maybe find the answer to my problem before bothering you. I think I've found the answer but before pulling the trans I'd like some input/advice. I have a 1979 Capri that has a 1970' 302 engine and C4 transmission. That transmission lost all gears 15 years ago, I installed a TCI pro super kit and it still had no gears. Took it to a rebuild shop told them about it and they did a rebuild (?) for me. Transmission was driven approximately 500 miles and it lost all forward gears and reverse was harsh. Went round and round with shop got my money back and lost interest in the car out of frustation. Fast forward to today my 15 year old son wants to start rebuilding it for himself. I pulled the pan air tested everything but the Intermediate servo (A) seemed ok, pulled servo found lots of sludge inside but non in pan. Cleaned servo reinstalled, changed fluid (flush) and with car still on jackstands it will engage in all gears and it will shift either manually or automatically, however when I put the car on the ground it does nothing but go into reverse harshly.The pump is pumping fluid but pressure doesn't seem very high.I plan on checking pressure, pulling VB apart, and rechecking w/air before pulling transmission out.Am I heading in the right direction? We plan on pulling the engine and transmission in a few months but would like to be able to just move the car around while we work on the suspension and interior.
Thanks for any insight you can provide, wish these forums were around 15 years ago.

Forward clutch is gone, tranny has to come apart and be rebuilt again.
Don't know about the harshness in reverse but I would loook at pressure regulaor for that.

I kind of figured that might be the problem.Like I said we'll be pullling everything anyway so it is either getting rebuilt by us or another one will be bought.After reading all the information on here I'm more comfortable in attempting this.

Thanks for your reply!

Pulled trans apart and found forward clutches wer shot. The #3 thrust is in bad shape, scored pretty good. Could not remove input shaft from front of trans had to tap it out from inside. It looks like it was rubbing against the #3 thrust washer. what would cause this to happen on a freshly rebuilt trans? Incorrect endplay?