Need Help Tuning my 318

I just started restoration on my 72 Dart Swinger. It needs alot of work but it always ran fine until this spring. I started it up and ran it for an hour. It started missing and running rough and no pull on acceleration. I found that a spark plug wire had melted and shorted out against the exhaust manifold. I bought new Wires & Plugs, still missing. I rebulit the Carter 2 Bbl carb and got a new fuel filter, still missing. Timing checks out OK and no Vacumn leaks. What am I doing wrong?

Thanks in advance
Rich :sad1: