ok, you want something SIMPLE, yet works.

have a platform for the generator to sit on. Make that platform HEAVY.
For my purposes, it does not need to be rubber mounted. Weld a plate
off the platform that goes sideways, and is at ground level.

drive the tractor so one front tire is on the plate. Hook the V-belt
up. Drive tractor forwards and backwards until it is lined up. Turn the
steering wheel to cure the skew. Eventually, you can weld a stop on
the generator to set the "depth" of the tractor by stopping the front
tire of the tractor.
Have a spring loaded tensioner on the slack side of the belt. Do not be
afraid to make this tensioner really stout, with a really strong
spring.

Now you have a rubber isolated (front tire) damperner, and it is easy
to hook and unhook.

Make sure your PTO can take moderate side thrusts.