Hi PBRme . . .

Are you by chance a Pabst Blue Ribbon fan?

If the holes go directly into the intake they are definitely for vacuum (for as C-Dan pointed out - wipers, brake-booster, distributor advance etc.) You don't want to put water or exhaust in there.

Check out the bottom of your intake. Does it have a place for it to bolt to the stock exhaust manifold?

If it does, then that is the place to fit a heat plate. You can use NPT to compression fittings to plumb water or you can run exhaust heat from the holes in the fentons (shouldn't have to weld anything to them). There's a guy who occasionally posts on ebay. He sells a very nice setup for this. As does Langdon's stovebolt.

regards,
stock49

[Linked Image from 49fastback.com]