Speedway motors, a mile from me & my former employer has many varieties of mandrel bends (appear to be good quality) & flat SB flanges but they ain't accurate (catalogue is online). If you need something cutout I would suggest Jerry at SD concepts, a member here, he cut some intake spacers for me & they were dead on. If I was doing that I would get some flanges cut so that with the stubs installed they match the head ports as closely as possible. EDIT The speedway flat flange cutouts do not not match the head ports, not even close.