I used 2x3 tubing for frame connectors on my '64 "B" body. Very easy to do and VERY strong. Had the car up on jack stands with all the running gear removed including fenders and doors. Doors are back on and close perfectly and the fenders aligned with no problems. The car was put on a rotisserie after the frame connectors and floor patches were welded in but that was for removal of the 60 year old undercoating and ease of assembly of the fuel system and brake lines.