based on the pictures and your posts, it has:
No Carbs
No Ignition
No Tank
No Seat
No Headlight
(and based solely on the picture) A rotting out exhaust.
I'd have to agree with the others that $600 is a bit rich for this machine. You say that it is $600 delivered, so if the seller lives 400 miles away, I could see that, if they're in town, they're asking too much (unless you know something about the engine that you haven't told us).
As for the Kawi tank, anything can be
made to fit. It depends on what you are planning on doing with this bike as to whether or not the kawi tank is the one you want.
Is the seller the one who has the CV carbs? If so, hold them up to the intake to see if they fit right on. If not, they're not going to do much for you.
As for parts, the key ignition will cost 25.00 plus shipping.
A Dyna ignition will run a little over $100, plus coils...