I've been looking for a unique engine MTH made back in 2004 and finally found it, problem is that its 2R. It has proto scale though. Has anyone successfully completed a 2R - 3R proto scale conversion? I've done some research, is my understanding correct that it's as simple as screwing in pick up rollers and flipping the 2R-3R switch? Understood no traction tires, different wheel flanges, etc. But if I understand correctly it should still run 3R and I don't plan to operate any tighter than 0-72. Any help would be appreciated.