I just got my rebuild completed and am buying my first spark plugs for the 30 over rebuild. NAPA gave me R43 AC spark plugs. The service manual says another number. What is the proper AC number for a 235 that is 30 over and was the original engine to my 1955 1st series 1/2 ton 3100? I know the R means resistor type, but what is the rest....44 or 45 or 46 and what does that mean? Thanks - Scott
