I was involved in doing the machine work for a big John Deere that competed in antique tractor pulls. The machine shop where I ran the connecting rod department on a part-time basis built up a welded stroker crankshaft by welding material onto one side of the rod journal and regrinding it for a 5/8" increase in the already long stroke. To fit that crankshaft into the engine case, slots had to be cut in the dividing wall between the crankcase and the transmission section of the block so the rods would clear, and a modified oil system was used to lubricate engine and trans from a common sump. The guy won his class regularly with that rig!
Even a stock John Deere will pull at incredibly low speeds, just by using the inertia of those big flywheels and that long stroke.
If you could get away with using a much shorter-profile tire, and/or smaller diameter wheels, you might game the system enough to drop your wheel speed by a pretty fair amount.
Jerry
