It's very easy to convert an old truck over to RHD, especially pre-1960 or so. There are indentations in the firewall, floorboard, and on some, the inner fenders that allowed the factory to build whatever was necessary easily. The only real mechanical differences on most is the headlight shift (LHD is to the right, RHD to the left), wiper sweep (usually the opposite, to conform with AU/NZ/UK/SA/JA laws), and the obvious things like master cylinder placement and such. No differences in instrumentation or even floor pedal placement (same as LHD). Shifting with the left hand gets a little getting used to, though!
A conversion on old trucks isn't a big ordeal.
