I just installed a new set of Champion rj12yc spark plugs which I have been using for years and THREE are fouled out.Is there a better plug for a hot 383?Here's the combo: .030 12.5-1 trw dome(heavy slugs) free floating pins zero deck block 906 78cc heads(bowl blended) 6-barrel setup(promax base plates) 509,soon to be racer brown sth-42 cam msd ign. 4-speed 4.10-1 gear