Check out Mike Scharlau's sharp puller, and see why I named his Gallery entry this way....
This pulling tractor started out as a 3314V Simplicity. I was lucky (bought the tractor for $275) that the bevel gear box and the vari-speed were in excellent condition ( the engine was not). I stripped the tractor down and repainted it to look like a 700 series AC, and planned on putting in a 16hp Kohler for a motor. Instead I bought a 1969 B&S that was completely overhauled with the biggest OEM piston put in to use until I found a K341 ( I haven't found a good one yet). I liked the idea of the variable speed even though all the pullers said to put straight pulleys on.
My son drives this tractor in the 800# Stock Altered class and I drive it in the 1000#. We have not had a first place yet but we have had a couple of 2nds, 3rds, and many 4ths. This is with as many as 20 tractors in our class! The pullers do not give out many secrets, and it has taken some time to learn our tractor. I have adjusted the vari-speed (VS) many ways to try to get the optimum range and speed from it. Last year we pulled in 2nd gear and I kept adjusting the VS for more speed until we run out of power; we did not! I now have adjusted the VS for slower speed and we are now pulling in 3rd gear on dirt tracks and blacktop, usually still use 2nd on clay tracks.
Last years points winner in 800# and 1000# was an AC B212 with a K341 engine. The guy sold the tractor is now running 7790 diesel, and yes, we beat Cub Cadets all the time.