A 366 (85mm) is the biggest you can go without spending big bucks. The machine shop in town screwed me for $120 a year ago to bore my last engine's cylinder out .040", claiming it was because of all the time it took to set it up on the boring bar. In their defense, they did a great job, and only do automotive engines, but, I won't use them again because of price. Most all cycle shops or machinests charge between 50&80. 85mm piston/gasket kit will run ATLEAST $150 from what I've seen.
You can go to a 400 if you contact CWR. That kit requires their special piston, and the cases need to be bored. Their website has the case boring listed at $50. I forget what the piston and cylinder sleeving runs.