Bruce, you ask an interesting question. Most of the information we have on these trucks is pieced together from several sources. The Reo 50V and the Sterling DDS235 Navy wreckers were essentially built to the same specifications. Both share the same Waukesha 145GK engine and the same transmission, transfer case, drive train, and Gar Wood US6 T26 wrecker boom. The cab and sheet metal, and the Sterling wood lined frame were the main differences. Reo literature refers to the 50V as a "10 Ton Naval Aircraft Salvage Truck", but the boom was rated at 10,000 lbs (same as the Federal C2) and the data plate stated the truck was a "12 ton 6x6 Wrecker Truck". There is no doubt the chassis is much heavier than the 7-1/2 ton Federal. The Reo chassis rails are heavily fish plated from the factory and the truck seems much more massive. The top of the engine valve cover is about 7 feet off the floor. A Reo factory image of the 50V next to a 7-1/2 ton Reo 29XS (same chassis at the Federal C2) shows the 50V to be substantially taller.
Both the Army Air Force Federal C2 and Navy Reo and Sterling had the same purpose, to recover damaged aircraft. The Air Force trucks were equipped with a 5th wheel and an underslung winch on the rear, while the Navy trucks were just a bare chassis behind the boom tower. The only drivetrain components shared by these trucks was the Timken T-77 transfer case. The Federal used the Hercules HXD engine.
There was never a wrecker built on the White 666/Corbitt 50SD6 chassis although some civilian operators added them after the war.
Jeff