john, thanks for taking the time to research this. from what i can tell the diesel starters are different,my brother tried to use a 88 diesel starter on his 880 diesel and it would not work and had to buy one for the 880,  but  the gas starters are the same and the starter from a 77-88 will work in a 770-880 if they were all 12 volt. this brings me back to the diesel bell housing and engine plate on a gas engine, i think a gas starter would work on this setup as long as you have a gas ring gear on the flywheel. what do you think?