I agree with rt01.
As I currently own about a dozen CB750's of similar vintage, you have to ask yourself if it is worth it.
The CB350 is not a rare bike, nor does it hold much value. However, if you were to do the work yourself and throw about $3000 into it, you would have a cool old bike, a little bike, with not much use, a bike that probably won't (or you wouldn't want to) go on Deerfoot with.
But, cool bike and there are guys that do collect and restore these bikes. Depending on how "complete" it is, EBay.com (not .ca) is your best bet.
Highly sought after items, whether you are parting out or selling complete - factory original pipes (non-rusted), gas tank with factory original paint (and no rust through) and side covers with factory original paint. Bonus item, good seat pan. Extra bonus item, good seat!! The rest of the stuff is still easily available (though disappearing quickly).
Post up some pics if you have, could help us make up your mind for you!
Otherwise enjoy dreaming about what could be.