Let's see.....convertible, 8.0 liter engine, hmmmmmmm.
I see a need for some more stiffening of the frame in torsion.
For example, GM A-bodies like chevelle and skylark had boxed frames for the convertibles, C-channel frames for roof cars.
R.
He used the GM front clip, all boxed. The GM rear clip 78-88 all boxed, and the center was original 47 Plymouth, rails boxed, X member was C channel. If He added a rear crossmember to the 80 Malibu rear clip, it should be pretty tough. The 78-88 GM metric frame was the go to frame for lower class dirt track cars for years, they held up pretty well, except for the center flex, which he eliminated. Gene
