South Florida FABO Brake mechanic needed!

I don't want to hi-jack this thread but I'll be watching closely to see what happens. I have a 71 Barracuda with non-power disc up front. I recently replaced the back brakes using new wheel cylinders and I'm having the exact same problem.

I can bleed the brakes starting with the right rear and all the air is gone. But let it sit for 10 minutes or drive it 100 feet and the pedal goes to the floor. Pull it back in the garage, the first squirt is always full of air then after that I get a nice firm pedal until it sits for another ten minutes. This is driving me batty!!

Anyway, so back in my hole to watch for the solution.