I always wondered why they went backward. The M48A2C I ran had a gasoline engine (Continental AV-1790) that put out 810 horsepower unless somebody jacked around with the governor linkage to let it pass that 2800-RPM max RPM.
Of course, the gasoline engine got only a third the fuel economy of the diesel - i.i MPG for the diesel, 0.5 MPG for the gasoline version. Many of us in colder climes lamented the loss ot the gasoline as it was superior fuel for tent heaters.
Another step backward from the M48 to the M60 was doing away with 'Little Joe', an auxiliary gasoline-powered generator. Little Joe meant you didn't have to keep the main engine idling while you were sitting in one place, something we found ourselves doing quite often. If you messed around and depleted your batteries to the point that the main engine wouldn't start, quite often yuo could electrically start Little Joe, and if you couldn't start it electrically, it had a pull-rope starter just like a lawn mower.
Probably more than you wanted to know, but every now and then I like to re-live my misspent youth.
old field guy