Shawn, most gages have a 1/8 NPT port and I just go from there. When hooking up your vac gage using at least 2+ feet will help It greatly reduces the "bounce" at idle and will have no influence on the actual reading. I have and have seen vac test gages that are plumbed from the inside with a barb only, this is not a constant duty type gage~thus the barb. A small SW works quite well and at 2 1/16 diameter it can be fit and/or mounted most anywhere.
Dave Neptune
