I don't know any of the technical specifics about the HT60 but I recently read in another thread that it is an upgraded version of the HT3B that is a bit more efficient.
I have a friend with a '98 auto that is using a 35/40 hybrid with an HT60. He just upgraded the head (fire-ringed) and transmission and his twin system by blocking the wastgate on the 35/40 and installed an external wastegate that dumps to atmoshere. So he's still tuning and tweaking. He's hoping to break over 600 hp using DDP3s and a 5K GSK. He's being guided by Lenny at DDP.
Prior to the recent upgrades he was using some Don M (F1 Diesel) performance 370 injectors, the stock wastegate on his 35/40 hybrid and a 3K GSK. He dyno'd at just a scoche under 500 hp last spring on that set-up.
-Jay