as regards rust proofing, of course it is better to do this than not. i think most everyone can agree on that.
as regards your particular situation, seperate needs from wants. If for example, the car will see limited use, is always garaged and consequently have limted exposure to the elements then the need is certainly low. i am not familiar enough with the car to know if the sills are sealed or not, but if they are this would further diminish the need to rust proof. As for what product to use, there are hundreds on the market. my experience with POR has been very good.
as regards restoration costs, for most main-stream cars, the largest item is usually labor. the hours spent stripping a car or sanding a fender is not dependent on make or model. Accordinly i would suspect the restoration costs associated with this project to be not dissimilar from your average 1961 international scout, 1962 MGA, mid-sixties corvette or 1970 ford bronco. if you are taking them all the way down to the shell or frame and starting over a lot of it is the same.