Welcome to OCC.
Like anything 40+ years old, a lot of things will need attention.
You mention motor mounts, there are 4 that look like sway bar bushings in a vehicle.
They can be anything from ok, to gone/nonexistent.
Also the "cradle" they mount too, is bolted to the bottom of the engine.
Those bolts give problems and often times one or more are missing.
Then there are the "Flex Disc joints" & drive shaft issues that need repair.
Best to use your eyes & ears to locate issues and address them one @ a time.
Does it run?
Do understand the 16 Hp kohler is a shaker.
It has a piston the size of one in a small block chevy and vibrates more than a Harley Davidson.
I honestly think Elvis sung "whole lotta shaking going on" in reference to those kohlers Ha,LOL.
You can search on this site for "motor mounts" also "cradle mods" for ideas.
The hydro fluid is prolly like a Slurpee in the rear end.
Change it and the filter as time permits, or immediately if you have issues with it.
There will also be leaks, squeaks & electrical issues to address.
Have fun.
