Matt,
I have NOS n360 pistons for sale plus used airboxes etc.
Please check out my webpage
www.geocities.com/kiwi_aircooled_honda_fan
I'm happy to negotiate prices and shipping etc
ps. I use 20w50 oil in my engine and it runs happily on 91 ron fuel. I guess your choice of oil will depend on the age and wear on the engine.
If you fit new pistons and rings you may find a thinner oil an advantage.
James