They use the stock, full-length bug frame. V-8 s have been shoehorned in, but often by removing the side panels from the hood. That hood is narrow and a 289 Ford would more readily fit than a 327 Chevy..
You see. I have a brand new, Glass Works 2″ x 3″ tube chassis, with a Mustang II front suspension, new (not rebuilt) Chevy 350, 330 horse (never been ran), 700R4 transmission, narrowed 9″Ford, 4:11, triangulatd 4-bar rear end in rolling condition. Currently, I have a 1969 VW Squareback body sitting on it. I thought a MG would be an interesting body to put on it. My chassis has a 94.5″ wheelbase. Wish I could get some specs on the MG or talk to some folks that are running V8’s in them.I am really computer ignorant and wish I knew how ro search this site or add pictures of my setup.