I second what JCoop said, use the 10W40 Castrol or Mobil 1. I have been advised to not use the
synthetic in these high performance engines. There seems to be some question about how it reacts with your gasgets. As for amount, just drain your
oil pan, replace your
oil filter. Fill your crankcase with the above mentioned
oil, until it approaches the "safe" mark on your dip stick. Spark it up, run for a couple of minutes, and top it up to the "safe" mark.
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"The 427 Cobra is easily the highest performance car ever sold for street use. A decent 427 - not the worst, not the best, will go from zero to 100 mph and back down again to zero in less than 14 seconds. All thing considered, you can put together a pretty good argument that the 427 Cobra is the ultimate performance car, judged on any basis you want to name." Taken from; Corvette, The Sensuous American
