Confused about my vin

I get the info about serial numbers directly from the old Kawasaki parts microfiche card issued to dealers direct from Kawasaki. I see the info on the other KZ650 info page lists 1980 KZ650B4 (E). Of course in 1980 Kawasaki debuted the KZ650E1 that was very similar to the older B series. I believe in 1980 there was no B4, and the 1980 KZ650E would be KZ650E in numbering.

RonKZ650 wrote: 533520 was the last serial number produced for the 1979 KZ650B3. That is what your bike is. There wasn't a B4, at least in the USA, and your bike is a USA model going by the engine emissions ports on top of the engine.

So if that's the case and the B4s weren't sold in the U.S. what parts should I get?
There seems to be slight differences in engine parts between the B, C, and E models, at least from what it looks like on Z1.

Get parts for a B3. Of course a lot of things not original on your motorcycle, but it's a B3.