duffer, glad the news is good for ya ! i remember using a late 70, early 80 ish booster, M or J, i can't remember which, on my 64 belvedere post car which required a slight ovaling of the original firewall through hole, and drilling a couple of extra mounting holes, and if i remember correctly, there was a stiffening plate, but that was way back in the late 80's, early 90's, so don't take that as gospel. my brain is loosing memory space. the car had a poly motor, and there were no clearance issues at all with the big diameter booster.