I was wondering what would be sufficient chassis stiffening for a 69 RR. Starting out with ~600hp, but looking at as much as 800 with future upgrades.

Currently it has the US Car Tool weld-in subframe connectors, as well as the Auto Rust Technicians (non-resto) torque boxes, front and rear.

Additionally, most of what I would call critical seams have been welded solid (shock towers, subframes to floorpans, etc).

I will be adding XV's tubular radiator support and inner fender supports.

Does this sound sufficient?

I guess my main question is do any of y'all think something like a "X" crossbrace between the subframe connectors would add anything besides weight? They would be bent to follow/mesh-with the floor. I have a feeling the high arch in the middle would really weaken their ability to provide any stiffening.

Maybe a bit of rectangular tubing between the rear subframes where the floor arches up just in front of the front spring mounts on the rear leaf springs? There's a spot that looks like its just made to put some 2"x4" rectangular tubing there.

It is mostly going to be a street-driven car, or I'd just cage it. I like the looks of a well-done cage in a street car, but abhor the door bars and loss of rear-seat functionality.

Any thoughts/opinions welcome.

Thanks.