I can't tell what truck you have?
If it is an AD (Advanced Design) then I would recommend the brakes I have on my truck, which come from a GM P30 chassis, like a bread truck. They allow you to use stock 55 and later 10 lug 20" wheels if that is important to you.
If you have a 55 or later then I would seriously consider the axles/brakes from a Chevy Top Kick, or a similar sized Freightliner, these are large hydraulic disc brakes with dual piston calipers. I used a TopKick front axle, and a Freightliner rear axle, both Rockwell brand, in a 61 F350, and they worked great. The truck weighed 10,000 lb empty, and I easily flat towed and safely stopped a 55 GMC COE that weighed something over 7,000lb, and an additional 3,000 lb in the bed of my truck, so total around 20-23,000 lb estimated.
I drove carefully, and did not need the brakes much, but if I did they were there and worked extremely well even with that much weight.
Reason I don't recommend the medium duty truck axles for the pre 55 trucks is the narrow width of the truck and the wide axles don't work out so well. The post 55 trucks are enough wider to make the larger axles fit, but with some work- usually involves narrowing the front axle.
Grigg
