WTB Intake vacume port for a 273

Unless you are doing a 100-point resto and need the original steel one, you can buy this item, made of brass, at a well-stocked hardware store. Pretty sure the thread size is 3/8" NPT. Hose barb size depends on what size hose your gauge needs; here's for 1/4" hose (you can use a 1/4" to 1/8" step-down adaptor after a few inches of 1/4" hose). Or here is a fancier one with a smaller barb on it.

Or you might get lucky and find a dealer willing to scare up a 4458 186 for you.