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.

You may want to repost this in the "Unlawful's Race Only" section or ask the mods to move it there if you don't get too many responses. Those guys will give you the best advice for your application.

Seems to me if you aren't going to be hitting it hard @ the track 90% of the time, it should be o.k., although not near as stiff as a cage would make it.

I'm adding 2" x 3" tubing against the full length and inboard of the US Cartool braces in my 66 Coronet convertible. I plan to also weld in shear plates at the 4 corners. The plates will incorporate the subframe connectors, crossmembers, torque boxes and rocker panels.

A street driven 69 w/600-800hp? What is your driving style? Have you upgraded the suspension to match the Hp levels? Brakes? Tires/wheels? Not sure if chassis is area most needed to stiffen yet? Is this a traffic light racer, or twisties? Need more info. XV front lower rad upgrade makes little sense to me in most cases until at the very end of upgrades, if at all.