Replacing Head Core Plug

You can also get mechanically retained plugs which use a "T" retainer (toggle bolt) similar to a block heater, although there might not be room in a head. You are not going to get a pressed plug in the rear of a head "in the car"

These are not the kind I was thinking of, but they work like this--with a toggle bolt

FREEZE PLUG, SIDE W/BAR, BILLET ALUMINUM

I would just go with a rubber expanding one until you can get the engine out. Put them in DRY and CLEAN, no sealer, which can act as a lubricant and "slime" it back outta there