SB standard or billet starter ?

I would NOT use a bush. That hole is larger.....for a good engineering reason. The starter has a three point mounting: nose fits into a machined recess + two fasteners.
The hole is enlarged so that the fastener for that hole can find it's own centre, to allow for manufacturing tolerances. Bushing the hole for a tight fit may stress the metal....& break the starter nose. When the fastener is adequately torqued, there is no need for a bush because the starter cannot move.