A NASCAR engine for the big leagues, the NEXTEL cup, will cost something near $100,000 dollars. Makes it very unlikely that anyone will have one in a street car. The block is a special casting, not like a stock Ford, Chevy or Mopar, except in the bore spacing, and probably the main bearing diameters, but not necessarily. The crank is also special, very light, and very expensive. The engines run for 400, 500, up to 600 miles at over 9,000 rpm, and can approach 10,000. The carburetors cost $1,100, and don't idle well, have no cold start provisions, and aren't easily tuned to meet emissions standards! The engines are built with 12.5 to 1 compression, which makes gas expensive and hard to find at the local station. There are other differences, too, in oiling, cooling, exhaust, ignition...