Hey guys, I'm new here and need some assistance. My father has a 65 Mustang with a small block V8. I drove it to my house to wax it for him. It was low on gas and had been sitting in his driveway for a few months. I drove it a few miles and put some gas in it. After about a mile it started back firing and really struggling off the line and in the lower rpms. I knew something was up and went back to my house. A neighbor suggested bad gas so we drain it and put new in. Still the same. Next I checked the screen in the carb but it was clean as a whistle. It idles fine but when reved at 1000 - 1800 rpms it ramps up and down. I ran out of time and haven't had chance to do anything else. What would be my next step? Thanks for any suggestions.