300ex power ups

[Moonraker]

I have a 93 300ex with WB head pipe and HMF slip on and a K&N filter with lid removed the carb is also jetted. I want to get more power so I can hang with my friends and their 400's I was thinking of boring it out and getting a HC piston, P&P job done and a cam I just want to do as much research on this to find the setup im looking for. Anyone out there that will give me their oppinion on what parts or any other ideas I should go with be greatly appreciated. Also, if i bore it out can i just have the stock sleeve pressed out then bore the cylinder and then get the bigger piston in there or do I have to put a sleeve in after the bore.
I mostly trail ride and hill climb.