Bill,No machining is necessary. The Series 21 piston fits in the Red Head liner. Take the Series 21 piston, head, rod, and wristpin and install in the RH case. Mount an APC 10.5 X 4.5 and go fly.
Everyone knows that Frank produces outstanding rings; however, he also produces wrist pin and crank pads. I have been converting McCoy 40 Redheads to McCoy 40 Hybrids. The Series 21 wrist pin used in the conversion always needs new teflon pads. I was pulling my hair out trying to find wrist pin pads. I contacted Frank on a hunch and discovered that he produces them.The pads are reproduced very exact and the fit is outstanding! Thanks Frank!!!!!!!!!