Disc Brake Conversion Failing

My car has the KH 4-pots and 10x2s out back .
she runs a 15/16ths M/C and 15/16ths rear-wc's,
and a booster from a mid-70s Swinger or F-body (I forget which)
She runs 235/60-14s up front and 295/50-15s out back
with Zero Proportioning.
She is far and away, the Best stopping street car I have ever owned, in 53 years.
BFGs got nothing for traction in the forward direction, but they do pretty good for braking....
She burns the rear shoes up a lil faster than the front pads.