Since you are interested in finding what core, if any, is unstable you, of course, need to run 4 stress test threads each with affinity to a single core. The one that (likely) fails is the crippled core, this core number is the same as in bios, as long as your bios counts them as 0, 1, 2 and 3.

The thing I don't get is why do you even care about the number of the crippled core?