Welcome back to "Flatland"
My first HD was a '47 too. but a (poorly) chopped servi..
Congrats on your '65........ second year for HD E.start
You got PM mail..
Did ya get the '65 from a gal (Karen) in Calif. ???
That's correct bore, std piston is: 2.743"= .002 clearance
They still sell to GP, but under Zoom cycle label..
And look here: flathead data