Thanks. I've been wrenching on various cars for a long time and it's sort of amazing how little I know. I'm pretty good on brakes.
To the present, never a dull moment. I got my shipment from Pelican today and the glow plug heat shields have a larger hole than the ones that came out:
Slightly different OD as well. The new ones:
.797; .394 (ID)
The old ones:
.811; .282
Both are .106 thick.