I am mounting 3/8 plate steel inside frame of my 1975 F250 to install power steering,I am using dom tubing as back spacers against frame.Four 9/16 bolts pass threw the PS box,threw the 3/8 plate and threw the dom tubing existing the back side of frame with welded plate.My question is what size dom tubing would I need for 9/16 grade 8 bolt to pass threw the tube.What wall thickness should i use.Thanks in advance to someone with this expierence