Another thing to think about: I know I'm always the one for worst case scenarios
Are you sure the #8 plug is being fouled by gas? It might be that your heads have a crack. Then the plugs would foul very fast and they would smell of gas, because the cylinder won't fire with water in it, so you have unburnt gas and water on the plug. Looks really yucky and stinks to high heaven AND means you'll have to tear the engine down. To test this quickly take out #8 plug and spin the engine. Hold a piece of card near the plug hole and see if anything comes out. Water will most probably spatter out if there's any in your angine, gas won't spatter, because it's distributed finer. Even small amounts of water standing in on cylinder for only about a week will ruin any engine. I had that happen to me on a 3 year old rebuild I bought (not my rebuild )
Do a compression check! If your cylinders vary by more than a couple of points, then you'll have to at least pull the heads and give it new gaskets. Otherwise you'll seriously damage something.
Holleys are very good carbs, but not so easy to tune and deal with in general as for example Edelbrocks.
As I said earlier, first check everything and try to find the error BEFORE you spend any large money on parts you wouldn't have needed in the end...
As always, that's just my opinion...
Hope this helps,
Max

PS: Give us your compression results on all cylinders if your not sure if they're good or not. A compression test will give you a rubish reading in all sorts of cases: Rust anywhere on the cylinder wall, cracks anywhere, blown or weak head gaskets, valves not seating, rings worn... Almost all internal engine faults will show up on a comp test, the test will only be perfect if all internals are in perfect order.