I used to make seat brackets, by using 2 pieces of alum angle one turned upside down and bolted to the seat, the other bolted to the upper one, then drilled holes in the floor where needed to mount the whole thing to the floor. That was on chevys, they seemed to have flatter floors than A bodies. You can shim to get a flat supporting surface, and even drill a series of holes for a tilting adjustment. You may have to make a pair or two to get it right, but it`s easy. They can be applied to a sliding seat bracket too, if u watch the heighth (size) of the angles. I think I used 1 1/2 x1/8" alum. angle.
