Check for rust in your fuel tank. My 66 began to be fuel starved until it would only run for a few blocks. I pulled the tank and dumped out about 2 inches of rust. The rust was covering the fuel pick up line. It would idle Ok but anything past that caused starvation. I coated the tank with a good gas tank sealer after cleaning. End of fuel delivery problem. I would check the size of the fuel line too like Griffin said.

55 Cabover