Won't go into first when warm/Reverse Grind when warm

Guys, please help. I installed a new centerforce clutch kit and new Ram flywheel a few thousand mile ago. Lately, the car is having issues when warmed up. After a few miles, when I shut the car off getting it into first is impossible. I have to put the car in first and start it. Also when warmed up the car will grind going into reverse. What the heck could be wrong. It is a 383 with a stock chrysler bell from another car. I looked at the fork and didnt notice anything bent or cracked. All parts are a few thousand miles old. Check the tranny that Passon rebuilt, perfect. I am about to give up. I fought a mystery problem with chatter a few years ago. That came down to pinion angle. Fixed that but that problem was another one where 5 or 6 items could be a culprit. It took me about a year to solve it. I cant go through that again with this problem. Please help or so help me, I am going to take the easy route and sell it to buy a model A Ford where you can fix everything with one wrench and a screwdriver. Ha ha ha