As the engine needed dropping 40mm below the bottom rails, I decided to drop the floor 40mm as well as I felt like I was sitting on top of the car. I used 3mm thick 50mm x 50mm angle iron stitch welded to the bottom rail, this added 12.75kg to the weight. The angle was welded to the inside of all the bottom rails of the drivers side but to the outer rails of the drivers side tunnel so I could run brake and fuel lines along it. A 2mm steel floor was used. On the pass side I just wanted the seat height to match. So I just lowered where the seat bolted in.
If I was doing it again. I would buy 2mm steel sheet, mark out where I wanted it bent and have the local steel yard bend it as this would save some weight, but not much. And it would be a better job I might imagine.
Seats bolt straight to the floor.
Hope that helps.
