The 6602 tops out at 2800, the military swapped both the Mack and the multifuel into the m39 series, a Mack made it a a1, the multi made it a a2, Of the three engines that was used in the 39 series, the 6602 GASSER had MORE torque and HP.
If you try for HIGH RPMS in the 6602, you WILL sling a rod, some diesel engine will go to 3500 or better, DDs really wind up, saying 2200 is the limit is more in line with the Cummins, the multi goes to 2600.