Thanks MatMan! Ok here are pics I wanted to wait but it's almost done.
First pic seat pans. A4's mounted low on top of 1 inch high 1inch hex stock, no sliders. More hex welded to pans between floor for seat mountings through bolts typical. You can't see it but in front of x-members the pan material has a 45 break bend to floor.
2nd shot detail of how the 6 bolts tie into interior crossmembers.
3rd, the block between the seat pans and floor.
4th, rear of pan.
Last, the before shot. The previous owner cut out the non rusted sub bracings to mount 55 pound seats each. Go figure....That's how this whole project started. To replace and improve the structure while keeping seats low back and everything light.
Seat pan holes are for great stuff/home depot spray foam for extra strength. Light and maybe some sound loss. When rivited the pans will be captured on all four sides with additional 90 angle on rockers, x-member and bend areas to the rear and tunnel.