do the proportioning valves fail?

2.0, wagon, manual trans, front disks, rear drums, no power brake booster

The rear wheels seem to lock up way before the fronts during a hard stop..

No dented or pinched brake lines.

I think that the previous owner installed the wrong master cylinder when he did a brake job. 

from what I have seen, in all of the catalogs, the Zone, amazon and evil bay all of  the master cylinders for 72-73 cars had master cylinders that were flat in the front and round in the rear and 74 up and MII had round front types.

mine is round at the front and flat at the rear like the 74 and later..

'planning to replace the master cylinder with the correct one and bleed the brakes, so maybe that will correct the problem.

thanks

Ed

All Pintos I've ever seen had a 15/16" master cylinder on them. Some have the number cast on them. Some you have to look in the sale catalog. But 15/16" it is.