Take a dremel to the sides of the screw heads and make two flat surfaces across from each other. Grab the screw by those flats with a small vise grip. If all else fails, grind the screw heads completely away, remove the sender, grind the screw stubs flush then reclock the new sender and drill new holes. There's a metal ring cast in the plastic around the sender opening.
75 Charger SE - 440/4, cop suspension
76 Daytona - survivor
76 Daytona - tweaked
77 PW - macho clone, sno-commander, frankenram
79 RC - this was your fathers 4x4
79 LRE - More fun than it looks