You can check out the picture at:
http://www.pelicanparts.com/techarticles/914_rogers_racing/DSC00019.JPG
which shows the gauges I have in my race car. As you noted the first two that were installed are in a bracket that takes the place of the ashtray. The top one was added (air/fuel) and right after I took this I found a neopreme 3x gauge holder from VDO that has the faces at an angle and put them all in line so I could see them easier. If you don't use the ashtray it's a good place to put them. Good luck