What's the hole in the intake for....collecting antifreeze

A pressure test will find it.
While it could be the gasket behind there leaking, it rarely is. It is usually the T-stat housing. Tissue paper blotting can also find the leak. Just blot the area under the stat gasket.The housing may need to be surfaced with a lathe-file, and the recess for the stat deepened.Occasionally the intake needs to be touched up too. I install studs in that location with fine threads up top. Then I use the washers that hold on the slanty exhaust manifolds, which move the clamp pressure further inboard.
Plus I only use a 7# cap. My hoses are all circa 1998 or older, and the rad is a '73.

Housings are repairable several times over.But at 7psi, the bolts only need to be snug.