X-Frame Stiffening

[CTX-SLPR]

Howdy,

I know that keeping the X is not a popular option, but I got what I've got and enough money for a custom perimeter conversion frame is not on the list.

I've been reading up, searching, thinking, etc... about how to stiffen the car up without having to built a complete custom frame. I was reading the thread about the Tunnel/Backbone frame on an early Tempest and that got me really thinking about how to potentially impliment a lot of the suggestions though with a full boxed frame already I'm not sure how much I need to apply to something like the underdash bar and backwards.
Similarly I read the Street Rodder How to Stiffen you Chevy Frame and while that seems like a good idea to reinforce the center of the X, I'm not sure how much it does for the overall stiffness of the car.
The idea I've come up with (and might draw up some evening over my long weekend) is to add a set of outer rails under the door sills since my inner rockers are rusted in a few places as are several of the underfloor braces. I'd tie the outer rails, that would hide where the inner rockers used to be, into the center backbone of the car with heavy 'U' channels to route the exhaust through on the passengers side. I've also been thinking of how to tie the firewall (and any under dash bar) to the upper spring pockets. Not sure if I should try and start the bars near the center of the cowl and then splay them out around the top end of the engine and downpipe on the passengers side to more closely follow the fenders then drop down onto the spring pockets or start out wide and just go straight down more or less. While I'd like to route a "Monte Carlo Bar" across the middle, unless I dramatically free up room with a new upper plenum under the hood, there is no space. Additionally there is a truely massive crossmember that runs between the spring pockets under the engine that I doubt a piece (or pieces) of tubing arching over the top is going to help to keep it from "squeezing" in.
For the rear of the car, there is a large stamped 'K' brace behind the rear seat that ties the parcel shelf to the inner wheel wells and the center of the floor pan at the rear axle kickup. There is also a crossmember, tubular welded to the top of the frame kickups, under the rear axle kickup and I put an angle iron cross member in front of the gas tank to hold the B-body tank in place and the rear stamped channel crossmember at the rear of the frame. Since this is a pillarless hardtop, and I am not willing to put a cage in that would add pillars, what can I do to stiffen the "hinge point" off of the firewall or any under dash bar? Run a pair of tubes down under the center console to approximately the center of the X for bracing? Box the A-pillars?



Must like with the Tempest, I'm after hiding all of this inside the existing car structure so it looks like a nice restromod on the inside vs. a birdcage protouring car. Opinions are certainly welcome.

Thanks,