I checked the frame# stamp and sticker orientation on a few examples I have which I am 99.9% sure are original:
1: 1974 Z1A Frame# stamped on the left side, sticker legible from right side, rounded corners on sticker
2. 1978 KZ1000B Frame# stamped on the left side, sticker legible from left side , square corners on sticker
3. 1979 KZ1000 Police Frame# stamped on the left side, sticker legible from left side, rounded corners on sticker
I don't think you should get too hung up on which direction the sticker is installed, after all they were installed by humans, at least in the case of the U.S.A. built bikes. (Japanese assemblers are more like robots!) From my experience I would expect more consistency of the sticker application on the bikes assembled in Japan. It makes sense to me to have the stamping and label legible on the same side of the bike for inspection purposes, but apparently they didn't follow that reasoning in Japan, at least on the 1974 Z1. I also checked a 1980 KZ750E that was built in Japan and the frame# on it is stamped on the RIGHT side, with the sticker also legible from the right.
Former M.E. at Kawasaki Motors Manufacturing, Lincoln, NE
1966 W1 (the Z1 of 1966-50H.P. and 100mph!)
1974 Z1A (disassembled)
1976 KZ900B LTD (SOLD!) it's in GOOD Hands!
1978 KZ1000 LTD
1976 KZ900B LTD pile O parts!
Still a little gealous, I’m looking for RWL tires for my 1976 Kz900 LTD. I can’t find any. I find the 100/90-19 S11 front but can’t find a matching rear. There was a NOS but it was 150/80-16. Not sure how old. What size did you find for the rear?