In fact, the manufacturer had an entire line of head-themed engines, including the Knucklehead, Panhead, and Shovelhead, with some featuring in the rarest Harley-Davidson motorcycles ever built.

The first is a 1955 Harley-Davidson Panhead sidecar rig. It has a ton of original parts, as well as plenty of OEM accessories. In fact, many of the OG parts are in boxes that came along with the ...