904 Transmission Stopped Going Into Gear

I rebuilt my first automatic in 1980. (I'm OLD). It was a 904 in a 73 Dart. No video, no internet, not even a book. I was lucky. Since then I've rebuilt more than a thousand Torqueflites. Now I have an ad on Craigslist rebuilding them for $400 all hard parts included. I buy cores for $50. I DO NOT repair hard parts. I throw junk parts in my junk pile for the junk man to take to the junk yard. You should look around for a V8 904 just for the HD drums. Your trans probably has three forward and three direct frictions. The V8 trans comes with four.