I have been using the NGK R5671A-10 stock number 5820, which is a silver colored or plated plug. I ran across some NGK R5671A-10 stock number 6239 which is a gold colored or plated plug. Question is: do both plugs read as well as each other or is one better than the other one for reading the plugs? I am having a hard time finding the stock number 6239 plug. Any suggestions. Roots blown hemi. PM me if needed.