Jeff, the 1st thing you need to do with the pistons is check piston to cylinder clearance and verify that its in tolerance, requires no more then a feeler gauge set,
insert the ring less piston up side down into the bore and see which feeler gauge fits (90% to the crank) in the void, compare reading to the FSM. if any are under you can get them knurled and the clearance will reduce. this is very important to eliminate piston slap.
As the mirrors go, I would use a piece of a wood dowel (a broom handle perhaps?), slightly undercut to fill the hole, finish with short strand fiberglass filler, sand to perfection.