1967 Other Chevrolet Models brakes locking

I have a 1967 Chevy 50 school bus converted to a RV. I put all new wheel clyinders and
brake lines on then started on a trip. After about 100 miles the right rear brake locked.
I loosened the brake and waited about an hour and went on my way. It happend 2 more times
in about 1000 miles. I re-adjusted all the brakes and stated on the way back. About 40
it felt as if the booster went out. Trying to pull over the brakes went out totaly. I
replaced the master cyinder and the booster and started out again. About 30 miles all 4
brakes locked. I opened the bleaders and released the pressure and got if off the road.
Now I have no idea what is wrong or what to do. I have been told everything from the
adjustment of the master cylinder rod to unhooking the vacume assist. I'm just lost and stranded in 100o miles from home.