^^^^^^^^what he sez.
But, since you are going from "weighted" to "unweighted', they may, may use a neutral-balanced wheel like a six needs and then balance it from there. And that would ONLY be on an automatic ('flex plate" is the term).
If it is an auto and appears symmetrical with the exception of some form of weight attached/welded/whatever
you could cut it off and use it on a six.
304 flywheel has a small (1" x 2"? ) weight CAST into the backside. I6 has 3 ribs cast 120 degrees apart.
If it's good TO you, it's gotta be good FOR you....