Hey! I’m back with another question about my car, I just swapped out a worn out 700r4 for a long cone turbo 350 out of a 74 c10 into my 1981 camaro. Car has a small block 305. Transmission was sitting a couple years so when I got it I changed fluid filter and gaskets, the pan had some clutch material but nothing unusual. On its first test drive I backed it out of the garage and did some laps around our property and then drove it to town with my father following me, it made it to town no problem, barely noticed it shifted into second but at 60mph I don’t expect it stayed in first, was running good when I pulled into a gas station and parked, we went inside and when I went to back out afterwards it wouldn’t move. Still had forward gears and neutral but no reverse, I can’t say 100% it had park as I was holding the brake anyway, but it was all of 10-15 minutes after I backed it out of the garage that it wouldn’t move in reverse. Any ideas?