In February 1954, 550-07 was assembled as a prototype 550. It was given to Wendler Karosserie in Reutlingen to demonstrate their coachbuilding skills. They wished to secure the contract for the upcoming prototypes and production cars. Porsche had not allocated a Weinsberg designed chassis (550-07) to this build, but one of the new Wendler frames (550-0043), from the supply allocated for Porsche customer cars. Porsche welded a new identification plate of '550-07' over the existing chassis plate '550-0043' already on the frame. This is the only 550 chassis known to have been renumbered.

550-07 was built as a race-test car for Porsche and was the first Wendler-built car on a Wendler-built frame. It was built as a Buckelwagen prototype, which consisted of a high rear body starting at the firewall between the rear of the seats and the engine bay. With a full-frame windshield and angled side windows, it was one of the most aerodynamic designs tested by Porsche test pilots.