Hemi heads on a poly?

There are 4 distinct poly engines and 3 distinct early hemi engine families. The Chrysler, (301, 331, 354, 392 displacement, 4.5625" bore spacing), Dodge, (241, 259, 270, 315, 325 displacement, 4.1875 bore spacing Desoto, (276, 291, 330, 341, 345 displacement, 4.3125" bore spacing and the Poly A engine, (277, 301, 303, 318, and 326 displacement, 4.46" bore spacing). For dimension details, check here

http://users.erols.com/srweiss/tablersn.htm

You can switch hemi and poly heads within engine families of the same bore spacing. The poly A engine does not have a hemi head made within its vintage, but it shares bore spacing with the LA engine and the new hemi. I have not tried it, but I have heard you can bolt LA heads to an A block. Not sure about the new hemi heads, but I can't see any advantage to putting these heads on an older A or LA block.