Was your engine set back all the way?
Probably?
I have never understood the people that say set back vs not set back. I dropped the LS in and bolted it to the stock 200r4 the car came with. I built my own mounts by just filling the gap in between the sbc frame mounts and the LS block. I then put the t56 in after a few months.
It's positioned the same front to back that the sbc that came in the car. The passenger side valve cover almost hits the AC box so I don't know how it could go back any farther and I have over an inch of gap between the truck PS pump pulley and the steering box.