Bill, I just had to post these "Hybrids", when I found them. I knew about some, but the others I didn't.
Greevesfield (Greeves- Royal Enfield)
250 NSU-Norton (NSUManx engine in a Norton frame) A waste, in MY opinion!
Norvin (Vincent engine in a Norton frame) BEAUTIFUL!
Norton JAP V-Twin
Of course, the Triton! (Wish the photo was bigger!)
Unity Norbstar (anybody heard of this one? What is it, hard to tell from photo. Norton/BSA/? ? Just a guess)
Got some more I'll post later on. Bill