If you wanted to go road racing in a Mustang back in 1993, Ford would gladly sell you this: The-one-year-only 1993 SVT Cobra R. The "R", naturally, stands for race. Nearly every aspect of the regular Fox-bodied Mustang was upgraded or stripped out to save on weight. The Cobra R was the fastest Mustang yet--capable of zero-to-60 in 5.7 …