This top end is the least of my worries on this bike. As I can go up to 6th over there are plenty of options. The fork tubes, transmission, the seat, getting things rechromed, repainted, etc are going to be much larger road blocks.
If the piston and bore does measure up I may just slap it back in there. As Sachs says, it does look to be in pretty nice shape. As I can go up to 6th over there are plenty of options. Of course putting the existing piston back into a bike I hope to have "new" in most respects doesn't really feel "right"...