I have the 11.75 fronts (stock 2.75" calipers) and 10x2.5" rear and manual brakes with a 1 1/32 master cylinder. Hard to lock them up...so I will switch to a 15/16" master cylinder, which will make the pedal force lower, but also increase pedal travel.
A stock mopar with power brakes has a 15/16" master cylinder. If you think the pedal travel is too long, then go up a little at a time. For your situation, the 1 1/32" is probably a good place to start.
IIRC, a dakota has a 2-bolt 15/16" master cylinder, and the diplomat (M-body) has a 1 1/32". The pickups have the big ones.