If you do it right, you should be able to do both mods for $500.

You could probably have a competant local shop bend up a 2 1/4" exhaust for a couple hundred bucks. If you're running stock logs the 2 1/2" won't met up easily and in any case is overkill for a mild 350.

That leaves plenty of money for an iron intake, qjet, carb rebuild it, gaskets, and coolant. With the remaining money, replace the points, sparkplugs, wires, and retime the distributor to get 36 degrees at maximum advance.

As for the 4bbl intake, yes you'll improve driveability and performance.

All these mods will improve fuel economy if you keep your foot out of it (like that's ever going to happen after you're tasted the new-found power).