Freeze Plug - 96 Geo Metro

My Geo Metro appears to have blown a freeze out plug. It is a 1.0 Liter 3 Cylinder. On the underside of the intake manifold there is a circular hole, proabably about two inch diameter, that water comes out of when I try to fill the radiator. When I went to autozone.com they had two main options with several sizes. The two main options were cylinder head, and block pipe. This does not sound like it fits either of those descriptions. Anybody know which one I should buy or have any other ideas? The plug is gone or I would use it for comparison.

I think a block plug should work out fine. It would be worth a try, before pulling the head.