I think JE pistons would be the best source if they make them. I suggest them because they make twincam pistons.
Otherwise, you could try some of the ring manufacturers, trw, sealed power,
Mahle, Hastings, etc.
On my last rebuild, I installed Deves rings. I think that is what RD supplies. I bought mine directly from Deves. They never seated and were very poor quality. Some rings had way too much gap and some would not even go in due to gap butting. Before jumping to conclusions, the bores were straight and to size (.020" over)
Anyway, after 1500 miles of smoking, I pulled the engine, ball honed and installed QED piston rings. No problems or oil consumption.
Btw, I have AE powermax pistons which have a different ring pack than the stock pistons. The Dave Bean catalog has a good description of the ring packs.
Good luck in your hunt.
