No doubt the bike is aftermarket
Pulling the tank the tunnel shows the bike was originally blue. I’m just curious what dealer or origin was producing these aftermarket KZ650
And the orange hand painted R C Pro Stock on side cover. Painted black someone did a handsome job pin striping the tank.
It did not work like that as far as vintage Japanese bikes, nothing like the car world special build houses. No Kawasaki 650 was ever done up like that from a dealership. Some previous owner had it done to match the RC pipe or whatever else they had done to the engine after they bought it. Is it "aftermarket" yes, I attached a picture of what a stock one looks like below as it would have sat in a Kawasaki dealership.
Usually you would order or purchase the stock bike from the dealership. If you wanted aftermarket parts you could purchase them and have the dealership mechanics install those parts before you took ownership. Very rarely would the dealership repaint the bodywork, that would be done at a outside shop.
RC and other companies were making aftermarket parts for the 650 but it was mostly exhausts, cams, piston kits. A lot of those company's no longer exist and there are very few aftermarket parts still available.
RC did more with Honda's then they ever did with Kawasaki's.