Cup type freeze plugs are pretty flexible- - - -they will fit a range of several thousandths without getting loose or leaking, and there's virtually no pressure or vacuum in a crankcase- - - -measured in inches of water either way! If it's a little tight, a drill press and a file or sandpaper makes it easy to tinker with the diameter- - - -especially with a hole in the middle for a bolt and nut. Loose- - - -a socket, a hammer, and a flat steel plate or a vise base makes for a good way to expand the diameter a little.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!