A Vista should be able to pull a 20 foot disk. My grandfather bought a 20 foot disk and G1000 row crop in 1966. It pulled the plow decently. They also pulled a 6 bottom mowboard with the tractor and lugged the motor (1500 rpm) all day long. The crankcase eventually cracked. The 585 should bolt right up to the Vista flywheel. A small bell HD 800 engine would also bolt right up, but could be tough to find. The G1350 and 1355 came with the factory 585 (on diesel). The 1350 is a little more rare. The 1355 is half Oliver (transmission and rearend) That Oliver transmission has 6 forward and 2 reverse (and a 3 speed powershift) for each gear. This gives lots of choice on gears.