Im looking at the same info....
A1 (1977 standard) models were manual
A2 (1978 model standard), A3 (1979 MKII), A4 (1980 MKII) were vacuum.
C1 (1978 police), C2 (1979 police), C3 (1980 police), C4 (1981 police) were vacuum.
The B1, B2, B3 and B4 models....which were LTDs from 1977 to 1980 are manual.
The D1 (1978) and D3 (1980) models, which are the Z1s are manual.
The E1 (1978) and E2 (1979) models are vacuum.
The G1.....which is the 1980 Classic model with fuel injection uses a manual petcock.
Likewise alot of the KZ750 lineup uses manaul petcocks....while some of the smaller bikes use vacuum.
There really isnt any rhyme or reason.....or year cut off for manual vs vacuum.....atleast not with Kawasaki.
As far as the 1989 ZX600....I dont even see a rebuild kit listed at Z1 for it. I see one for the 1987 ZX600 and its vacuum....so Im guessing that your likely correct that the 1989 ZX600 is vacuum as well.
.....but there are alot of KZ models....and they differ drastically in the small parts. All I know for sure is that they did not start using them in all of their models in the mid to late 70s......not even close.
Mine is a 1980 B4 model....the LTD....with a manual petcock.