[Dave Gantz]

I'm guessing a proportioning valve, with bias to the rear brakes has been tried?

I had a car that had factory front discs, and should've had 10" rear drums, but it had 11". It would lock the rears wheels when it had street tires on it, but stopped nicely when the slicks were on it.

Of course, the fronts usually do most of the work, but in this case, the rears did and the slicks made it work.