At an early stage, it was suspected that once the war was over, the Packard Motor Car Company would be unlikely to continue the manufacture of V-1650 Merlin engines. Furthermore, the Allison V-1710 had by that time matured into an engine which, without a turbosupercharger but with two stages of gear-driven blowers could give excellent performance at high altitudes. Consequently, the V-1710-119 was specified for the third and fourth prototypes, which were to be designated XP-82A.
The third Twin Mustang prototype (44-83888) was completed as the XP-82A and was fitted with a pair of Allison V-1710-119 engines of 1500 hp each, driving propellers rotating in the same direction. This change to the Allison brought the Mustang design full circle. The serial number was 44-83888. The Allison installation now looked not unlike that of a Merlin, because the -119 engine had an updraft inlet and an injection-type carburetor upstream of the two-stage supercharger, so that the inlet was on the underside of the engine behind the spinner. The inlet was about a foot further back than with the Merlin.
There is no evidence that the XP-82A was ever actually flown, due to problems with the Allison engines. The other XP-82A prototype (44-83889) was cancelled.
Serial numbers of XP-82A
44-83888/83889 North American XP-82A Twin Mustang c/n 120-43744/43745