Replace the fuel filter, get it to not leak. That leak could turn into an air intake under power (suction) and putting air into your fuel lines. Plus being that close to the exhaust could very well cause vapor lock. Start by replacing the fuel filter/fixing the leak. Chances are it will eliminate the vapor lock but only time will tell.
Oh, and you will get gas all over yourself, the truck, your tools, the ground. Gas is the greatest when it runs down your arm and finds its way to your arm pit. And when you get some in your eye, that's even better! I'm gonna go drip some gas in my eye right now just to relive that sensation again....
And what shop does a tune up and doesn't replace the fuel filter? Also brings the question, why did they replace the carb and not rebuild it? I would be hesitant to go back to that shop again. They may be a decent shop for newer cars where you just pull a diagnostic code and replace a part but these old trucks and their carbs are a different animal than anything on the road these days. Diagnosing these old beasts is becoming more of a lost art than anything else.