Originally Posted by 64fleetside
I show 555-002 or 555-129 Dorman 7/16 steel, or 550-002 concave type, also steel-book does not show brass available in that size. You could also drill/tap to a plug size like 3/8 NPT.

Thanks fleetside, it looks like steel is the way to go here. Steel freeze plug that is.

my pet peev...socialist earthlings.