On a waste spark system you should use double platinum plugs. Because the cylinders fire on the compression stroke on the positive side and the exhaust stroke on the negative side, copper plugs would burn out very fast. As an example, double platinum plugs are advertised as 100,000 plugs, but I wouldn't go past 50,000 miles due to the possibility of the plug getting stuck in the engine. The copper plug on the same engine would only go about 15,000 miles. Based on the locations of the plug applications on various vehicles, I would not want to change plugs every 15,000 miles.
A distributor less system with waste spark.
Could be a bad ignition coil either traditional type or C.O.P. (Coil on Plug) type
The plug gap is calculated to match the energy of the ignition system, the plug type and the compression and displacement of the cylinder.
.035 for points type ignition and .045-.050 for duraspark ignition
From .044 to .028 depending on: year, motor size, ignition system, fuel system, plug type.
A '94 Civic CX uses a distributor based ignition system.
.035" is factory using standard point type ignition.
It depends on the type of ignition. probably 32-35 for points type and 45-60 for electronic ignitions.
It depends on the type of ignition system you have. Some have ignition coils at each spark plug, or coils for each plug away from the plug, or coils for every 2 plugs, or a single coil for all plugs. So the coil could be bad, or perhaps simpler the spark plug wire could be bad, or a bad spark plug. If you have a distributor it could be the cap or the signal rotor. There are other possibilities including the Electronic Control Unit, and electromagnetic interference (not likely).
Let me know the type of heads you are putting on the 302 and if they are 2V or 4V heads and if possible what type of vehicle was this 302 originally in. Spark plug gap for my 2V truck is .044
My 73 Bonneville has points type ignition. The later years had electronic ignition distributors, which had .045 or more gap. If you're engine is points type, the gap is .035.
personally I would use an iriduim plug.