Call Ross, that may not be a custom piston, they will do changes to a shelf piston for a small cost, which saves money and time. I needed a 4.50 bore for a 4.25 crank which was not a shelf piston, they took a 4.5 stroke piston and just machined the compression height to fit my needs. They also gave me an order number and let me buy my pistons through summit and that saved me $100.00 after their tech guy and I went over the measurements.
Diamond will make (I think) two changes to a shelf piston at no extra cost. Better call and ask before taking my word on this as it's been about six years or so since I ordered mine.
