Bdoggy,
That is where I put my test gauge to measure block pressue. I will plumb my permanent gauge in the same location.

I do have an adjustable pop-off relief valve mounted of the front of each engine to help control water preasure, but not so sure I needed them, but sometimes you never know until you water test the boat----it's just that they're A LOT easier to install them when the engines are out of the boat and while you are routing the plumbing. The drain cock is also where I have a -4 hose connection going from there all the way up to a gauge on my dash for each engine.