Len, if you're still looking for one, I've got an OS .52 that came off a J-3 ARF; has maybe 4 flights on it. The airplane really needed a .70, although it flew fine with the .52. Has a solid aluminum spinnernut on it right now, tho I've ordered the replacement original nut, prop washer, and locknut for it. They'll be in the middle of this coming week.
I was gonna use it on a Goldberg Falcon 56, or a Skylark 56, but both projects are on hold for quite a while yet. Too many others need finishing before I get to them.
It's in excellent condition. $100, plus 5 bucks shipping, CONUS.
J.D. Channelview, TX J.D. to e-mail, pull the post