A buddy of mine has the 94-95 on3 kit on his 331. He opted to upgrade from the 70mm standard turbo to the 88mm ball bearing one they offer. It seems to work pretty well, and the install wasn't that bad. I know he ended up having a new oil feed line for the turbo made because the one that came with the kit was no good.
I also have an on3 kit in my 95 GT but I swapped a 351w into my car, so I went with the 351w fox body swap kit for my application. I had to modify a few things to make it work in my sn, but that was to be expected. The only big thing I have to address is the hot side piping get in the way of my front sway bar, so right now, I don't have it in the car, but I am currently in the process of making a custom one.
My buddy's car is currently making 490hp to the tire on low boost but it will be getting cranked up as soon as the new clutch goes in.