If original, the motor should be a GMC 302 or 270 CID gas engine. They were mostly the same as civilian GMC motors of the same displacement. Easy to ID by engine number on block behind distributor - first 3 numbers are the displacement. Military blocks may also have a data tag on lower front of block on the passenger side. Most were not machined for a fuel pump.
Multi-fuel came later but not on 270/302 motors.
Jack
www.inliners.org
