When I lived in Phoenix, Arizona, U.S.A., there was a guy at Deer Valley airport who converted one or more T-6 aircraft into the P-64 version. It involved turning it into a single-seater using turtledeck, changing the engine to an R-1340, add guns (fake for a civilian plane), clipping the wings a bit, and strengthening the airframe in specific places to cope with the extra power and speed. It would cruise at 250 mph, right with the Mustangs.
Real P-64s were rare. Some had the straight-line tail and some had the curved tails. The main distinuishing features are the R-3-1340, 3-bladed props, single seat, clipped-wing.