fouled plug = broken head stud or worn valve guide?
 

I'm in the process of gapping my plugs, could a fouled plug be any sort of indicator of a broken head stud or worn valve guide? if so, which?

Usually a fouled plug is caused by excessive oil burning so worn guides or rings can cause this.
Broken head studs have different symptoms.... Chuff Chuff sound etc.
(If in doubt take of your rocker covers and check the head stud nuts)

But fouled plugs can also be caused by a car that is "idled" for prolonged periods during storage.