Sorry, but I have never bought any gauges for my boat. I suggest you post to "Ask All Sailors" on the main sailboatowners.com site.
Just a few more thoughts about installation. Personally, I'd go with mounting them in a recessed coaming box with a seal, or at least provide certainty of water protection. The surface mounted gauges in the 9.2A in my other post look pretty, but I doubt they will age very well in the sun.