[Cobra #3170]

Yes, I did the only thing I could do that would not impact the original appearance. I had two steel tube prepared that had the same outside diameter as the main frame rail inside diameter. I had a vertical member that was .180" thick rosette welded into both tubes every 4" on both sides the full length, then ground smooth. The tubes gained considerable bending strength from the "I" beam configuration. We cut the caps off the frame in the front and forced the tubes inside the main rails and rosette welded them in place then ground the welds down, welded the front caps back on and painted everything original black.
It added 100 pounds to the car but it was well worth the effort. If the floor is slightly uneven when it is on jack stands there will be a gap between the floor and jack stand at the low spot even if it only .060. The car is approximately 300 % stiffer now. Although that sounds huge it isn't, original cars were terrible. Jack them up and the doors would jam. Adding torsional stiffness really helps with everything especially chassis tuning.
You can actually feel a 25 pound spring change now or a slight change in anti roll bar settings too,