Freeze Plug Size for back of Block?????

[Buick455truck]

I need to know what the freeze plug size is for a Buick 455?
The one behind the cam. I'am not sure of the size. I think i'am getting the wrong numbers.

Thanks for the help........I'am a first time Buick 455 builder!:grin:

[Buick455truck]

:Do No: Please help, I need to know very soon.

Thanks