This is a little off topic, but I have an old "Choppers" magazine, with a picture of an engine with a BTFH bottom end and a shovelhead top end (and I don't mean a 45 bottom end with a sportster top end). Whether it actually ran or not, I have no idea. But, it is still kinda cool looking.
I have seen several of these hermaphrodites. All of them were built by "Williams Motors". Mike Williams started doing them in his Van Nuys, CA shop back in the 70's. William's Motors/Iron Eagle is now located in Canyon Country, CA. Joe at William's may build one for you, but don't hold your breath waiting for it.