I'd say the GP290 kit would be the easiest route and gives a good power hike,just a simple head and piston swap,the kit comes with all gaskets,gudgeon pin,circlips,piston and ring aswell as a sparkplug,they aren't that expensive either and mated with a rear Dom have quite a dramatic effect on overall power,its one of the better options if on a budget and keeps the 28mm stroke which in my opinion is better than any 30mm stroked engine....
