body mounting
 

Hello people I,m rusty ford AKA Dan I,m installing a 52 f1 on an s10 frame and i was told that I can not drill holes in the top of the frame.It would make things very easy if I could,there are 3 reinforced pieces that go across the cab that the original mounts tied to,I would like to run 5/8 inch bolts with isolaters made from 1 inch belting threw the floor and top of frame.My daughter is a B pressure welder ,so if any one knows what I would have to do to properly reinforce it to make it legal it would be genuinally be appreciated.Thanks Dan

5/8 sounds a tad beefy. I don't see why you couldn't drill the frame as long as the area/s were reinforced, plate, boxed, doubled etc. I'd doubt there is a legal build design to follow, but making sure the frame isn't weakened with some iron added on in those points seems it would suffice..

I believe you are referring to the frame flanges .
It is a generally accepted practice to not drill any holes in the flange area. What is done where bolt down surface is desired is to mount a holdown on the side of the frame/chassis . Your welder can fabricate the holdowns to accept any size bolt you choose.