Engine VIN question

Ok. I bought a 1980 KZ750-G LTD. Went to working on the carburetors today and noticed something that looked like a VIN stamped into the right side of the engine. This is the number:

KZ750BE052232

The frame VIN is as follows:

KZ750G-006110

Did somebody put an engine from an older twin on my bike? If so, I'm actually kind of happy - much easier to get parts for a '76-'79 twin! Thanks for your input.

The motors are identical anyway, there are some differences (depending on year models) between the charging systems, carbs, and the 82-83 models had the air ports cast in the head for emissions.

All the 750 twin motors start off with KZ750BE, even the 82 motor in my 79

ok, thanks steell Now I have to go back to worrying about the original owner's "carb rebuild" :S