Bigchevy3600...I'm assuming that your are talking about your
3/4 ton (hence the 3600 des.) ! No one out there makes a disc brake conversion that I'm aware of (I've tried Brothers, Cl. Pts etc.)...
I did install a power brake unit from CPP & it works quite well !
I have a '53 GMC 3/4 ton with the 8 lug rims, I'm running a 350 Chevy engine with a turbo 400 auto, I mounted the booster under the frame w/out any problems ! You will have to reroute
the drivers side exhaust with 2 bends... Cpp gives you great inst.
on how to add the unit ! Hope this helps...