WM-300, the 4BTs are almost all H1C turbos as far as I can tell. Any GM version low mount turbo is a H1C with a non wastegated housing that is 16cm2. I just got a high mount turbo off a ford version with the centered exhauist manifold. I thought it would have been a H1C but I am not 100% sure, it is a reman unit from Cummins, and looks like it may possible have a 18 cm2 exhaust housing because its's big, and the turbo itself seems awefully small, though I still hypothesize that it is a H1C. Hope it helps. The good 6BT turbos for 4BTs I think are a '94 WH1C with the wastegated 12cm2 housing. But pull off the wastegated housing (if you wish) and use a non wastegated housing. Or the Hy35, which is a bigger turbo with a small choked up wastegated 9cm2 housing. that is what I am using...
Andre with Toyota Land Cruiser in Utah originally from Keene, NY.