Maybe someone has run into this before

Maybe someone has run into this before. After I bought the truck a year ago I had to replace the heads (new rebuilt heads) and found that when I got further along that the cam lobe on #6 was completely worn, no lift whatsoever.I didn't have the time or place to replace it so I got a mechanic to replace the cam and lifters. It had a miss before, but chalked it up to the cam. After the work was done it still had a miss to it.I put a new quadrajet on it because i'm trying to stay as original as I can, and the miss is still there. So what next!I was thinking maybe bad valve on the new head, or distributor, but the miss has no rhythm to it (i.E. 123-miss-5678) it is sporatic. Correct me if i'm wrong, but if it was the head or dist it would have a miss at the same valve or point on the dist over and over!The only thing I can think of is fuel. New lines, tank, etc. Anybody have any suggestions?Thanks