There is no reason the studs in the spacer would be the same as those for the vehicle, either in thread or part number. Are you running 1/2-20 lugnuts?
That said, most OE studs have a three digit number on the head which you can cross reference through the Dorman website
here. The Dorman part numbers for wheel studs is 610-XXX where the "XXX" is the 3-digit number on the head.
If that doesn't work, then pop out the offending stud and post up the thread, underhead length, knurl diameter, and knurl length and we should be able to figure out what you have or find a suitable replacement.