AC Pulley for 273 or slant 6?

A number of years ago a friend gave me a bunch of '65 Barracuda AC parts. I am going through stuff now trying to make space and selling what I don't need, as my car does not have AC and I don't plan on installing it either. My original 273 4 bbl from my '65 FS is on the stand, so I thought I'd try to mount up this pulley just to make sure it fit before I offered it to the group, and to my surprise, the bolt holes don't line up. They're close, but not right. The center hub fits fine though. I started looking through the parts book and it gets confusing when it comes to AC parts, and now I'm wondering if it came off a slant 6 instead of a 273. Is there any way of knowing, I don't have a slant 6 so can't test fit on a 6 crank. Someone on the list may need this part, so I hate to toss it out. Any suggestions?

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