I know we are always looking for a 12v glow plug, and it seems all the numbers can only be bought online and expensivish.
Locally carried by CarQuest, NGK 6628 (Y-107V) $7.49 each 10.5v
I replaced my (thought were 12v) 6.2v plugs today, worlds difference! Though I'm sure they were half burnt out from running 12v
They are slightly different but fit perfect in my 4d56