ANDREW - I agree with Matt & Kraig. Dave R knows his Kohlers but if it was me, I'd still only bore the K301 as little as necessary to get a good round straight cylinder.
With some porting, maybe a cam, planing the head, careful tuning, a K301 can make good HP and still be fairly efficient. The OHV engines will always be more efficient, it's all a matter of Physics, but the cam timing and tuning of the old K-series Kohlers towards low end torque makes them a great working engine.
I built up a K321 to the Killer Kohler spec's about 4 yrs ago and put a K361 cam in and if I had it to do over again I would keep the stock cam. The longer duration really effects the idle & low rpm performance. But once you wind it up, which only takes a fraction of a second since it's a small flywheel engine, It's a BEAST.
Yeah, I'd say a 147 compares really well to a 140, the little deare has the hydraulics & steering brakes. The CC 149 was able to get hyd also, up to two spools. The hydro drivetrain is BULLET-PROOF. I have steering brakes on my 982 and they are handy sometimes, but who ever uses brakes to stop a hydro?
The variator is kinda a neat feature, but they seem to be like the Torque-Amplifier on full size IH ag tractors, they work awhile then need repair. Except the T/A's last longer. The GD CC's are just about totally bullet-proof also. The biggest problem you will see with them is the 1/4 in. dia roll pins breaking/shearing in the front of the rear drive coupler on the larger HP tractors. And the mating 1/4" dia hole on the back end of the driveshaft egg-shapes about every 1000-1500 operating hours, so many make their own driveshafts from prehardened 4140 or Stressproof steel round bar. Not sure how long those last, Nobody has wore one out yet.
STEVE B. - Thanks for the RAMMING Speed pic's. Yep, things have sure changed....even in the last two hours. I don't have any drifts as big as KRAIG's.... YET. But Mother Nature is still working on them. Just heard the weather girl say they had a 53 mph wind gust in RACINE, WI. I'm happy for them! Snowing an inch an hour there too.