There isn’t a single pre-1970s tech engine that can fit in the Abrams that will be able to move the tank at the current speed and acceleration requirements.
The Honeywell/Lycoming AGT1500 used in an Abrams makes 1,500 hp and 3,950 lb-ft of torque.
Additionally, NO piston engine could meet the multifuel requirements. The British came closest to doing it, but their Leyland L60 turned out to be a giant disaster. Nobody else even tried.
“There isn’t a single pre-1970s tech engine that can fit in the Abrams that will be able to move the tank at the current speed and acceleration requirements.”
Okay, then we are back to square one as I doubt there is space on the tank to fit an pre-1970’s technology engine that is powerful enough to move the tank even at slow speed.