Mike,
I had a similar problem this summer with my 351W,tried everything with fuel system, changed jets ,lowered fuel level, raised fuel level, advanced timing,retarded timing.Nothing worked.Friend suggested.Did you check you dist. cap? I dismissed him as a fool and went home and checked inside the cap. Loaded with moisture.I dried out the cap and dist. and car is running perfect. Guess I was the fool.
Cranky