I have a 73 K2 (topaz orange) that I think has a pretty solid engine (compression) but is missing a bit of everything else. I also have a 72 K1 (candy yellow) that I picked up with a seized piston. Everything else about the K1 is solid and complete. I have removed both engines. I want to keep the K1 as close to original as possible, so I didn't want to drop the entire K2 engine in the K1. However, I was thinking about putting the K2 top end (cylinder and head) on the K1. Are the digits "Hm D4" on the K1 cylinder unique to that year? I didn't want to mix up the parts if they are year specific.

Thanks ahead of time!