Well, this isn't exactly what you wanted but I did I similar thing to what I'm thinking you want to do.
I like the bigger gauges (2 5/8") because they are easier to read. I bought the a-pillar pod from Poston's to hold two 2 5/8" gauges. Got a liquid filled boost gauge from autometer along with their 2 5/8" tach. Mounted on the a-pillar, they are easy to view and now I have a tach without some giant honkin thing attached to my dash. From what i remember it's a 10k tach too. not that you'd need that
Just a thought. Hope it helps a little