I tend to tinker more with the diesels. I can beat many tractors that have more cubes, but I know my limits. I can get my UB diesel down to 6500 pounds, but I almost always pull in 1st gear. I don't have the hp to jump to 2nd gear. I intended to build it really bad with some 5.125 pistons, but I couldn't make that work, so I went to some stock MM pistons. That was 12 years ago, and I have had fun with it ever since. Most of the pulls I attend give a trophy thats worth about $5, but its fun to beat the red and green tractors. Its important to keep the fun in this tractor pulling thing.
Remember that power is not the only variable for a good pull. You also need good traction and a well balanced tractor. The G1000 FWA was really neat to pull as a demonstration. having the front wheels helping, changes the whole traction equation. You just can't make a gas tractor smoke like that. Happy pulling everybody!!!