i have 1975 el Camino, what will make,my transmission?

Old threads in the block may be slightly loose. Next time you have to tighten them pull each out and put a drop of Blue lock tight on the bolts and reinstall, torque to the proper values. Should stop the loosening wiht use.

if you don't have the correct flex-plate/flywheel, it is vibrating too much and causing the bolts to back out. Otherwise, go with the lock washers, and RED locktight.

put lock washers on the bolts or use lock tight on the threads ! if it comes down to it you could replace the bolts with self tapping bolts !