Hey I gaurentee to weld to the floor pans youll eventually crack the pans when the chassis twists to the torque It will cracknext to the weld. They will work OK for a while,but will crack.
How bad do stock floor pans crack at the back of the front subframe mounts, and the front edge of the rear frame boxes, where they all tie into the floors? The point of subframe connectors is to keep the front and rear of the car from flexing, twisting and torquing... the stress points are where the front and rear subframes meet the un-framed body/floor pan. By virtue of the fact that we're talking about subframe connectors, we admit these are highly flexing areas, hence the need to install something to eliminate that flex.
Have any of us seen badly cracked floor pans? (from cars that WEREN'T raced every weekend from 1970 to 1977 :-D )
If those highly stressed areas aren't cracked from what the cars have been through, the contoured subframe connectors welded the entire length of the floor pan aren't going to crack the floors.