XJ550 Maxim engine rebuild

Hello - I will likely come into a 1982 Yamaha 550 Maxim that my father in law parked in the mid 90's. It will likely need an engine rebuild and was wondering the following:
1. Does anyone know where I can get new pistons?
2. Does anyone know if the block can be bored for 650cc or 750cc pistons and where I can get these?
3. Are there stock or high performance cam shafts available to buy?

Thanks,
Frenchtom