That's a model 28 and it's an AVS motor (Anti Vibration System). You'll need an ARC #6280 rod and use the stock piston. You'll need the ARC #6561 brass crank weights to replace the AVS system. It's a tricky deal because some of the older cranks have the removable eccentrics, the newer cranks may have to have some machine work, OR just buy the ARC #6562-C crank. Then you'll need a cam....I suggest an E.C. Cams #400-276 for a basic decent running cam. Then you'll need a flywheel and hub...ARC #6611-AVS for the flywheel and ARC #6611-AVS for the hub. You can use the stock ignition coil I think, but for that flywheel you will need to use the Briggs starter #845759. Don't forget a set of valve springs from E.C. #260, clean up the intake and exhaust ports for better flowing, leave the stock rockers on it, set the timing respectively you'll have to re-jet the carb, run a full exhaust, not just a piece of pipe off the exhaust port (this is where so many people mess up)....then you'll be set for a nice running motor in the 6000RPM range. I'd advise for you to put that kind of money into a 31 or 33 model motor to get the most out of your money. Good luck and have fun!
~Joe
