Clean Out Plugs

[Throck Morton]

You appear to have the correct plugs. 8CM-6307 cross references with your Dorman number. They are supposed to be .628 in dia. Or more likely a metric plug 16mm (.6299 )
I always installed them with a loosely fitting pin punch, or a steel bar in the center of the cup. And a 3-4 lb hammer !
If the punch fits too tight you will have a difficult time removing it as the walls of the plug collapse in from the press it.