Like 440 offroader I used a HB off a 2000 Cummins truck, but since mine is a diesel I couldn't use it as is because it's too long and hit the intake elbow. I made a flat plate to mount the unit to the firewall and shortened the pushrod. I used hoses and master cylinder from the 2000 truck as well as the power steering pump to get the two return nipples. You can just tee off the single though. Now I guess the ticket is to get the entire assembly off 2500 GM van, (a "G" I think) that already has the flat plate and is supposed to bolt directly to the firewall but the pushrod eye is different. This unit clocks the HB and master cylinder differently and probably needs custom hoses. Both will need M/C to proportioning valve lines made.
You can buy a reseal kit for the HB off ebay, they all take the same kit. You need a special tool to remove the pushrod though if you plan to change that. The big nut that holds the HB unit to the bracket is 1 7/8" I believe, but don't quote me on that.