next size available 25thou a time i think,dependent of piston maufacture and availablity standard bore honed is a clean up usally re-ring it can use old valve train if condition correct spec check valve guide tollerance or renew as well as new inlet seals. reseat valves and decoke full gasket kit renew big end and main bearings may need new synchros on the box or bushes may have gone s/hand maybe a better optiontest b4 buying get a workshop manual
stage 1 might mean stiff pedal, B series the same apart from cable clutch type,exeedy or honda best tested to 240 hp john banks honda do good deals may PP to your place,its a full kit
perhaps take bottom pannel off under gearbox clutch housing to see if a broken clutch cover spring falls out. or anything else for that matter. maybe uneven spring pressure on the clutch cover if so also worth measuring deflection of slave cylinder when pedal pressed and set correctly