No, the A3 variant uses the same CAT motor as current the generation FMTV(family of medium tactical vehicles) 2.5-5 ton trucks in military service. The A3 was a special conversion of the common M35A2 "deuce and a half" that used the engine and transmission from the FMTVs and added CTIS(central tire inflation system) to the axles. The original King Kong used a Continental multifuel (typically run on diesel) engine. I'm guessing it's just easier to use a more modern engine than worrying about the temperamental older versions that are harder to source parts for.
The plan with the new truck is to look like the old truck but with the modern motor for reliability and maintence. Most any of the military trucks going to auction now have been remotored with Cummins or Cat power.