When I made the intake manifold for my 250, I built the carburetor bases for Rochester Mono-jets. Once I figured out they didn't perform like I wanted, I switched to Carter W-1's. The bolt spacing is different so I made offset mounting studs. All I needed was one for each carburetor. I simply cut a stud in two, off set the two pieces, and welded them back together. I then cut a spacer with the correct bore opening for the W-1, flared the bottom to match the manifold bore, and slotted one bolt hole in the spacer to clear the offset stud. The spacer is about 3/8" thick.
