Personally --- I would do a direct swap for the 3/4t setup for the series your truck is. If you have a GMT400, swap for a GMT400 and then you don't have to worry about the setup working with your vehicle. When I did mine and built the parts list for everybody, all the parts were from a 3/4t suburban. Perfect fit w/no mods.
if you can find it - I wound up going with a GMT800 setup for my 98 K1500. it takes modification here and there, it is not a bolt-in, but it isn't as hard as solid axle swap. I used parts from a 2004 Suburban with HB, and got the HB unit and the hose from the HB unit to the gear box. I also grabbed the pedal and the gear box, and I bought a "new" (reman with reservoir) pump and the pump-HB hose. I later acquired the P/S cooler from another 2004 Suburban, and the GMT400 version as well, but I haven't used either one yet - I have a 12x12 plate cooler that I'm going to try first since I'm also running a hydraulic winch.
highlights:
- the pedal is worthless; the GMT400 quadrant is very different from the GMT800 pedal quadrant, and simply swapping pedals is not possibly without a LOT of drastic modification.
- the HB unit actuator rod (the rod with the eyelet that connects to the pedal) is too short. you need to measure the length of the rod from the vacuum booster, and then cut off the eye on the HB unit. At this point, you thread the remaining rod of the HB unit, and then cut off the eye on the vacuum booster (or perhaps a junkyard unit, so you have a backup plan) and thread the eye and screw it into the coupler nut.
- once you fix the length problem, I was concerned the brake switch would no longer be compatible, but this was not the case - it went back on just like factory, and the clip too.
- you DO NOT need the gearbox, but I grabbed it to do a gearbox swap in my truck. this requires further modification, but will work - otherwise, the gearbox you already have is just fine, and the fittings are all the same as the GMT800 setup.
- the hydroboost pump for a GMT800 is the same pump that has been used for 25 years, and can also be used on a Vortec engine with no mods; this is handy if you plan to do an LS swap later.
- the GMT800 lines were too short, at least the pump to booster line was. get lines for your truck base don your year/model with hydroboost. (or a 3/4 ton equivalent).
-if you haven't done the NBS master cylinder swap, now is a FANTASTIC time to do so. I have no idea if the GMT400 master works with the GMT800 HB unit, I already had a GMT800 Master cylinder.
I still have a few more things to do since I'm plumbing in a winch, changing the gearbox, modifying the intermediate shaft, etc. basically, stuff not having to do with the actual Hydroboost installation.
