A couple notes about doing this swap:
All of the 61-71 D100 pickups use a 5 on 4.5" bolt circle for the wheels. Dodge did away with the 5 on 4.5" bolt circle when they went to the D150 series in the mid 80's and went to the 5 on 5.5" bolt circle. So, if you do find a later D150 series front suspension to use, getting a set of rotors for an 84 D100 will get you the 5 on 4.5" bolt circle and it's a direct swap no modifications.
Also, and this really has nothing to do with the IFS swap. All your 8.75 rear axles can be upgraded to 11" x 2.5" brakes by swapping backing plates and drums from a 9.25 or any 93 and earlier rear end. The same applies for the bolt circle if your running 5 on 4.5" use the 84 D100 drums and your good to go.
Mark D.
1968 W200 Sweptline
1969 D100 Utiline
1971 D100 SE Sweptline
1993 D250 Club Cab Sweptline
1986 W250 Cab & Chassis
1978 D300 Sweptline
E. Brookfield, Massachusetts