BARRY - I agree with everything KEN says.
If you can get cyl. wear corrected, Taper & out-of-round fixed with only .010" O/S save the extra .010" for another rebuild in twenty yrs.
I've never replaced valve guides but know some people who have. They have to be installed "Correctly", reamed to size after being pressed in. And valve seats ground concentric to the new guides per the spec's too.
I've NEVER heard of one of those huge roller main bearings going bad in a Kohler. Never replaced one either.
I've used STENS parts, but for a real "Working Tractor engine" I use Kohler parts. And it's always recommended to deal with this forum's sponsors. They make this forum available, give good deals, and will be around in the future.
And not to stir up old "Discussions", those balance gears Ken refers to make nice paperweights for your desk.
It's also better to have the engine "hot-tanked" to really clean the engine inside & outside before starting to reassemble it. And to install all new seals & gaskets, points, points pushrod, condensor, spark plug, and clean & rebuild the carb. And have both the Kohler engine manual and IH service manual available for reference when assembling the engine.
Basic hand tools will suffice for most of the work. Things like a ring compressor, valve spring compressor, feeler gauges, flywheel/harmonic balancer/gear puller, maybe a caliper or mic help. I normally use two torque wrenches, a 0-75#/ft for all small fasteners like head & rod cap bolts, and a bigger 0-250#/ft for the flywheel nut.
LOTS of clean shop towels, cleaning solvent, assembly grease/lube, and mounting the engine block to an engine stand makes assembly easier too.