NHC250 is 250hp/ 685 lb-ft@1500rpm, 8.3 is 240hp/ 745 lb-ft@1500rpm . 923A2 weighs 1200lb less than a 923A1. I've heard better reviews about the 8.3 trucks as far as acceleration, but don't have any first-hand experience. 60 lb-ft should make a nice difference though. Op manual lists the NHC250 trucks getting 3-4 MPG and and the 8.3 CTA trucks getting 5.5-6 MPG, so that's a plus for long trips. The 8.3 has an adjustable fuel plate like the 5.9 so power changes can be made pretty easily. Higher HP 8.3 injectors are available too. I plan on leaving it stock though.