Definately no '79cb650.
Things to spot(to my eye) that are telltale signs of a '79 are the side covers, look at a couple stocker pics, and compare to 750/550 or other 650 pics, you will see what I mean.
The turn signals are mounted off the grab bar, not off the brake light assembly, frame or the rear fender.
The tank is definately unique on the '79 650 as well.
Look at a '80/81/82cb650(SOHC) and compare to a '79.... BIG difference.
Another is looking at the seat, the '79seat has a slight rise for the passenger seat, the '80 and newer have a more pronounced rise for the passenger seat.
Also the '79cb650 (in the US) came stock with the reversed stamped comstars.
Not spokes, and not the standard comstars found on bikes such as the '79DOHC 750.
Good luck finding a '79.... I'm trying to find a mate to mine.... I always wanted twins.
l8r