Bryan, carringb, an OP here, tried several high-tech approaches like frozen/drilled/slotted and found that late model OEM Ford brakes worked best. Companies convert Ford Vans to 4x4's and this leaves take-off parts which are often new. QuadVan (call John)in OR and Quigley in PA (call Doug) come to mind. They do this mostly on new vans which are then delivered to retail Ford dealers. Another company, U-Joint Off-Road near Asheville NC (call Chris), does one-off's for customers and they too have take-off parts. My Quigley "kit" was the twin axles, bushings, ball joints, radius arms, rotors, hubs, calipers, pads, ABS sensors, and a few steering linkage parts.
Be sure the conversion place you call knows you're working on a DUAL rear wheel vehicle. The Front Hubs are different, to allow for the different style of wheels used on Single- and Dual-Rear Wheel vehicles. They're only selling you the FRONT, so it's easy to forget.
You can rebuild your front end and gain superior braking for less than many alternatives. Bryan swears by his, and results on ours were excellent.