Zack in addition to What David has told you here are a couple of previous conversations that might help you. I bought all the stuff to hook up the mechanical gauge but have not done it yet. I have screwed the T piece I got from Merlin Motorsports into my engine and it fits just fine so I do know I can tee in the mechanical gauge with no problem if I get to the point I am not trusting the stock gauge set up.
David
68 E-type FHC