Finding no takers for the Pioneer III coach, Budd re-worked the design into an Electric Multiple Unit for commuter operations by fitting a propulsion system and a vestibule type operating cab at each end. The Pennsylvania Railroad's increasingly antiquated fleet of MP54 suburban MU's prompted the railroad to order 6 Pioneer III MU's from Budd in 1958. Measuring roughly 85 feet in length and 10 feet in width, the Pioneer III coach resembled the stainless steel coaches used by the Pennsylvania Railroad for its premier New York City-Washington, D.C. and New York City-Chicago services. Seating on the Pioneer III was in two rows of 25 in a 3+2 configuration. Like all m.u. coaches, the Pioneer III was capable of running as a single-car train or with up to six cars total, depending on the number of passengers it was to carry. The Pioneer III car had an advertised speed of 100 m.p.h., but in actual operations ran at speeds of around 80–85 m.p.h. Its knuckle-shaped (tightlock) couplers, identical to those found on the PRR long-distance trains, allowed the Pioneer III coaches to be transported to shop facilities in Paoli or Wilmington for maintenance. The original numbers were 150-155 with the even-numbered cars having fabricated truck frames and disc brakes, while the odd-numbered cars had cast steel truck frames and tread brakes.