I'm not sure what that means "decked" . On the rear of the block where it bolts to the bell housing, at the center is where it says "GM8" then a few inches to the drivers side, it almost looks like something was removed from that spot, like hammer marks almost. Not sure what that's all about. What I've been reading is "hi perf" and "pass" means that it came from a passenger/truck suburban type vehicle. Again, not sure how accurate that info is either. If money wasn't a problem I'd just buy a new motor, tranny and rear end.....