A lot of us running Chev Gen3s down under are using the T56 with it's Hydraulic Throwout bearing setup. I believe their HTO is made by AP (There was an AP in the casting of one I removed).
They do tend to turn the fluid black but I'm not sure why. It hasn't affacted the performance yet and it's pretty easy to flush the fluid through.
We've had couple of problems with them. The first was the size of the line from the M/C to the HTO. Most of us are running braided lines and initially used #3 Line. This was to restrictive and slowed the fluid returning to the M?C after releasing the clutch. The clutch would slip a bit until the returning fluid was pushed back. Switching to a #4 line fixed this problem.
Finding a M/C to suit was a problem too. You need about 11 or 12cc of fluid to disengage the clutch. Most have settled on a 1" bore cylinder. I found a 7/8" with a slightly longer stroke and it works great. The pedal is light which is important for me as my left knee is stuffed. I've also got a heavier after market pressure plate and coper/ceramic puck style clutch.
There's no adjustment on these HTO setups though so adapting them up to another application would mean machining shims etc. As your clutch wears your engagment point will change. The original pressureplates where self adjusting but that has proved troublesome. A adjustable pedal is a better solution.
Cheers