If there is no lip at the top of the cylinder then your bore is stock and the pistons should be correct for that. A big bore engine has alot of piston clearance. I have heard of putting Bon Ami in the bore to seat the rings haven't tried that so can't say if its safe or not but sounds like it would work.
On my 45 LA I have the high compression LP pistons and head and I had to go to 12 volt battery to turn it over.
I can still hand crank it though but I'm strong for my age (68) I like to get young men to try to crank start it you would be suprised how many can't.