This is the gauge I used: Auto Gage 2177 - Auto gage Analog Gauges - Overview - SummitRacing.com
There is an adapter required as well, less than $5. I can't remember the p/n, call Autometer and they can tell you.
I would also suggest possibly getting a 45-degree fitting. I don't have one, it works without it, but that short lower intake bolt is almost impossible to access with the gauge there. I think a 45-degree fitting is pretty inexpensive, I will probably get one sometime in the future.