I have an all original '72 CB350 twin in excellent shape that I purchased a few years back for $1000.
With those parts missing, and assuming it's titled and running, I'd pay about half that.
They are fun bikes though.
edit: Nevermind, I just re-read and saw mention of carbs not included. Thus, it wouldn't be running. Those parts are going to be (most likely) on the pricey side (the exhaust and carbs in particular).
Unless you could pick it up for a few hundred bucks, I'd pass.