Before you pull the engine apart and spend a bunch of $$$, why not try lowering the total timing some more? You said it ran good with 6 initial and what was it 26 total? Try dropping the total down another couple points, if it runs good you wont have to change out the cam. If a lower total makes the initial too low to idle properly, you can always modify the distributor to give you more initial with less total, or leave the distributor un-modified and use manifold vacuum for the vacuum advance to get the idle advance higher with the total lower. Doesn't cost anything to do that and if it works that could save you some cash. If it doesn't work your only out some time.