I have seen both Mark and Jeffs cars and realize that they are running the drag pak engines. Even talked to Jeff about this at Indy. My info came from Bruce Bachelder, NHRA Tech services, at the Southerns. As I understood it, the rule was put in place because there were some late model LS1 or LT1 firebirds that ran with the same motor and the Formula scooped hood with different HP rating so they ruled that the hood and engines could not be mixed. Looks like they have at least changed to allowing air engines in non air cars in SSGT, maybe both ways by now.
I would still check with NHRA before I built an engine/body combo for SSGT.