Roll Cage Question for TechInspector

I'd like to build a removable NHRA legal roll cage for a 31 roadster on 32 frame rails.

The cage proper isn't a problem, but the attachment points are or could be.

Thinking is to use gussetted 1/4" C.R. plate and weld the roll cage to these.
The plates would be bolted to frame pad points with two 1/2" grade 8 bolts at locations equivalent to what's required for a welded in cage.

The frame pad points would be welded in place, stepped threaded bungs to accept the roll cage plate bolts.
These threaded bungs are larger than the holes they are inserted into and would not pull through the frame even if not welded. (The frame rails are .120 fwiw.)

Alternate thinking is a 1/4" plate with threaded bungs inserted inside the frame and welded in place with holes drilled through the frame to allow bolting on of the roll cage.

At the front of the floor - at the toeboard - I do not wish to cut into the body's sub-frame (the sub-frame is standard Model A) and would cantilever the front cage mounts inward from that area.
Cantilevered meaning that the front cage mounts are in a tapered box with appropriate threads. They would sit inboard with the bolt threaded bungs centered about 2" from frame center.
The frame at that point is 2" wide.

Granted, perhaps a pain in the backside to set up such a cage, but the car will only hit the nostalgia races once a year or so and remain on the street most of the time - and running a large diameter 4-point roll bar there.

Thank you Mr. Tech.

I thought it would be a viable deal considering the plate mount setup clamped through the body sheet metal on frame-less cars.

I think the pad and backup piece would be stronger than simply welding to the 1/8" frame, but I can see how that wouldn't be a go legal-wise (NHRA legal) until considerable testing was done.

Looks like I'll have to find another roadster and start another project - strictly for racing - once the 31 is on the streets.

Things could be worse....:)