Like my signature says, I went with ISSPRO guages, based on response from the DieselStop forum. There are cheaper, but these will last forever.
The boost gauge merely tells you how hard you are being pushed back in your seat (when NOT towing). But it also tells you when you are consuming fuel. No boost means driving using little fuel. My transmission guage mounted in a test point in the transmission. I had my BIL, a machinist, come and drill and tap the hole for the Exhaust Gas - that was a little trickier than I wanted to do. I could have bought matching paint for the pillar but it was maybe 10 bucks. I got a pretty close match at Wally World $2. The entire job took me 1/2 day, plus a couple hours for the BIL's work. (That cost me a couple beers.)
I was surprised at how hot the Exhaust gasses get, and how warm the tranny will get on an extended run during the summer. Well worth having the guages!