You'd be lucky to run five minutes on a tank of gas. The gas is only used for starting. Not much power in gas mode.
This is not a put-down. The tractor is meant to run on diesel and start on gas.
If the tractor runs well, it is worth several times that of a gas powered SMTA. If it has serious engine problem, it will very expensive to fix.
A restored SMTAD can sell for $15,000 - $20,000. A high crop sold last year for $45,000.