Most likley a 396 chevy small or big block, some of you may be thinking oh 396 thats a big block,,, not in all terms,,, theirs small block chevys making 472 CI.
I betcha is just an S10, most people dont go out of their way to spend good money to turn a 4.3L V6 turbo, into a 396 twin turbo race truck.
Those turbos are very large to be spooling even for a V8, im sure its going to have a 4000+ stall converter.