MG Car Repair: 1973 B, platinum plugs, copper core

Question
Hi i was reading that an R spark plug is not recommended but to use a boschW6DP or NGK BP 7evx. I saw this a few times on All Experts.Will this help me tune my B, i currently have Champion RN9YC. Your advice would be appreciated.

Answer
Hi Andre,
I found that you are asking for trouble when you use a resistor plug on resistor wire so I don't like to use them. If you look at the spark plug books in most any auto parts store you can pick the features that you want in a plug. As I remember most of the "Bs" came with Champion N9Y. The "N" is the reach (3/4") and the number is the heat range. I think the "Y" is a projector core which is ok too. All the other letters are other features. The reach MUST be kept correct and the heat range must be correct to the factory specs or you can use a step colder but never go hotter. Also the heat range numbers are different on each brand of plug so you MUST get a comparison chart to switch brands. The "C" for copper core in an NGK are ok but I have no use for platinum plugs.  
Howard