Ford, Chevy, MOPAR and a few other manufacturers all used 4" diameter pistons over a span of several decades. As long as the rings are the right thickness to fit the piston grooves, those rings won't care what brand of engine they're running in. Don't let somebody sell you some sort of outrageously priced rings when it should be possible to find over-the-counter items that will fit. Even if you buy a set of rings for a V8, it will probably cost less to discard a few rings than pay a king's ransom for a custom made ring set.
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!