Spark Plug Help

[mudjnky]

I need help trying to find the right plug for my engine. It is a GM crate 454, I believe it is the 430hp version. It has the cast iron heads and is probably a version from 3-4 years ago. It was in the car when we got it and someone changed the plugs to a different number last year. They are fouling out due to bad carbs and I want to put the correct plug back in the engine. Is there anyway to find out the correct plug for the engine? I emailed a couple of GMPP dealers and got no replies.

[Chevy454]

What heads? Just a guess, but I'd say they're *probably* an open chamber w/ tapered seat spark plug...sound about right?? If so, something in the NGK UR4 or UR5 range would work...