I echo Randy's comments...get it running and stopping and see if it's the truck for you. These trucks were not designed to go as fast as we go now days.
What kind of loads will you be hauling?
As for different gears, there are none. If you want a faster gear ratio you'll have to do a axle swap to something newer.
IF you're lucky you 'll have the 22.5" tubeless wheels, if not you'll have the 20" tube type widow makers.
The standard engine was the 235, the optional engine was the 261.
The 4-speed will be the SM-420 (granny gear 4-speed).
The rear will be the 13,000 pound 6.17:1 single speed as standard issue or the optional 15,000 pound 6.17:1 or 7.20:1 single speeds, or the 15,000 pound 5.83/7.98:1 or 6.40/8.72:1 2-speeds. Hope you have the 5.83 2-speed, but with the 16,000 GVW I'm betting you have the 13,000 pound standard issue single speed rear...the Army liked to keep things simple.
Mike B
