WTG Jugman, It's an R2000-7. We overhaul these for the RAAF in Australia. It's used on the Caribou. During the war, it was used on the C-54 Skymaster (DC-4) aircraft. It's actually a R1830-94 that has the cylinder bore increase by 0.25 for additional displacement. It used plain bearings vs. the R1830's roller bearings. The R2000 was manufactured by Pratt & Whitney and Buick.
IFF52nd