When you want to change the stroke on a crank there are some general things that must be done, first the engine must be disassembled and basically rebuilt. So you need new bearings, seals, gaskets, and a rod kit. Then the crank is sent to TNR Machine for stroking which involves boring the crank pin hole, sweating in a slug and boring a new pin hole farther from the center of the crank journal. Then the cases may need to be bored to accomodate the off-set connecting rod, and of course the head must be recessed for the greater piston travel. The port heights and ignition timing may also need to be altered depending on the stroke change. Its quite an undertaking and the variable in the cost are things like tranny bearings and parts, clutch plates, or anything else worn in the bottom end. Generally speaking its cheaper and more effective to big bore the top end then to increase the displacement with crank stroking.