I'm going to have mine rebuild and my mechanic related the following to
me. I'm sure it's not complete, but it may give you some idea.

rebore cylinders
new pistons and rings
check bearings and crank
possibly regrind of head
new gaskets seals etc.
check conditon of valves, springs, retainers and cams.

I'm sure there's more, but the above I think covers the bulk.

Good luck,