In the middle of an engine rebuild for my 1965 Valiant 200 Wagon. There's a plug in my cylinder head and the plug is cracked. Tried the suppliers I've used in the past (Bernbaum, Roberts Motor Parts, Kanter) but no luck. Any idea where I might find one?
The 1965 Mopar parts catalog shows no freeze plugs (also called core plugs or soft plugs) on the slant-6 head, only on the block. There is a threaded plug in the head for vehicles that didn't have the optional heater.
There was a head redesign in 1974 where it got one freeze plug.
I don't think that this is a freeze plug. Can you find and post a picture of it from the internet?
If it's a threaded plug as IC describes, and you can remove it, you might want to measure the thread size (if you don't have the device for that, a parts store might), then see if you have any strong bolts in your bolt jar or on your work bench that are an exact fit. Or buy one from a hardware store. That might work until you find a supplier that has the correct OEM or after-market plug.