Did i damage my 727

Sounds like it has a slipping front clutch. How does reverse hold? What is the history of this trans?
Is your kickdown/throttle valve linkage hooked up and adjusted correctly?
Reverse holds good I think got to give it a little more gas but probably the stall right? don't see a issue with it. I got the trans from a buddy that didn't know anything on it but when I pulled it open it looks clean and everything looked alright so I buttoned it back up. It has a shift kit in it I noticed as well and I have a 3k stall