The floor is made from a sheet of 3/16" plate , welded all around to give some stability to the body. There is a crossmember that spans from side to side, made of 2" x 6" oak, to act as a rear body mount to the frame, and the rear bolts on both seats are thru the crossmember, but that was purely coincedental.(actually I drilled and tapped the plate for the 5/16" seat bolts)