I just bought a used 1979 Mercury 150 hp power trim V6 and looking for spark plug recommendation help the book says use Champion L76V or AC-V40FFM but reading that NGK most are saying run much better can anyone plz lead me in the correct direction serial number on mount says 5130069 but cannot find a parts diagram on this motor so any info would be greatly appreciated??? other number found is 1579-6606 don't know what number to use for a parts diagram .