I have 7 blade 18" mech fan with thermo clutch, and fan part number #2863216 from my 72 340 Challenger. I was using it on my Duster w 408 and found a crack in a blade so need a replacement fan. I find two aftermarket fans available and I don't need number match in the moded Duster. Hayden 3618 or Flexalite 5718 which are both 18" 6 blade fans for clutch mount. Has anyone used either of those, do they fit stock clutch, and will they cool like stock fans.