Here's the thing, a foxbody can be many things. It could have been a 16 second beater, or 9 second car in street trim. They're one of the biggest "what if" cars out there.
They fact that it had a cage "could" mean it runs 11's or better, or could mean nothing at all. We've all seen riced out civics with ghetto ass cages.
OP, says his GP pulls just as hard as a car that runs low 12's @ 108. Whether or not that's true, the kill story is believable...at least to me.