Frame Stiffening

[Brads70]

Another option to the US Cartool SFC is to make your own. I bought the USCT SFC then sold them after I discovered how much work it was to fit them up to the floorboards and after I had a good look at them I figured they were only as strong as the narrowest point. Meaning they shrink down to suit the lower part of the floor boards about the same as the square tubing I used.   The other reason is IMO this design is much easier to reverse , just cut them out and grind down the welds. Another reason is square tubing is MUCH cheaper than the USCT set up. I think I had $15 in materials to build my own but that was 10 plus years ago now? 
I used 1x2 square tubing ( 1/8" wall) then I used 3/4 tubing and drill holes every 8" or so then welded them in. This made a big difference in torsional rigidity with very little weight added. 
The USCT set up does look really nice when all finished.
As always it is a case of plus and minus to every decision. Just thought I'd add in some food for thought... 

[Brads70]

I did use the USCT firewall items. Well built IMO , material is a little thicker than necessary  though IMO. I didn't bother with the under the rad parts though. Instead I build what some call a Monte Carlo bar to tie in the shock towers. Yes, someday I'll repaint my engine bay.... 
I did also make my own LCA plates, I believe they do help. Not so much for handling but to tighten up the control arm bushing socket slop.

[HP2]

Brad's point reinforces that the non-contoured type connectors  can demonstrate a  big improvement in rigidity.

I've had the same experience in my cars back before the fancy kits were available. I've had cars where you couldn't open the door if you jacked up one corner of the car. Installing even a cheapy connector and things were solid enough  that panel alignment never changed and doors could now be opened when the chassis was wedged unevenly.

[Filthy Filbert]

I did use the USCT firewall items. Well built IMO , material is a little thicker than necessary  though IMO. I didn't bother with the under the rad parts though. Instead I build what some call a Monte Carlo bar to tie in the shock towers. Yes, someday I'll repaint my engine bay.... 
I did also make my own LCA plates, I believe they do help. Not so much for handling but to tighten up the control arm bushing socket slop.

Do those install over the stock braces, or do you remove the stock braces and add those in?

[Brads70]

I did use the USCT firewall items. Well built IMO , material is a little thicker than necessary  though IMO. I didn't bother with the under the rad parts though. Instead I build what some call a Monte Carlo bar to tie in the shock towers. Yes, someday I'll repaint my engine bay.... 
I did also make my own LCA plates, I believe they do help. Not so much for handling but to tighten up the control arm bushing socket slop.

Do those install over the stock braces, or do you remove the stock braces and add those in?

Yes they go over the stock firewall braces.

[rhamson]

If you are doing a pristine number matching restoration the frame connectors and torque boxes will bother the selling aspect of that car's definition. If it bothers, you then either sell this one to buy one it won't bother you with.

[rhamson]

You should do what you want the car to handle. Ignoring the added torque and horsepower add-ons could bend the car out of shape and regardless of originality you may end up with an original mess to unload if you don't.