HP, TQ and body twist

[ss dave]

I have a 69 Camaro convert. It has the cross member and subframe connectors that are welded into a notched lateral frame and the front/rear, new suspension thru out. Hooks up well now but planning on adding more HP & TQ. I hope the experts can give me some advice on how much HP/TQ the car will handle before I have to worry about body twist. Doors, lids shut great with smooth lines and I would like to keep it that way. A roll bar is a consideration, I believe this would help- but is it necessary? I know Frank at Prodigy has built some cars with crazy #'s and a few verts, what do think? thanks