I use the ScanGuage II in the Crossfire. It works just fine and reports all the usual parameters. During the "off season" it is in the Avalanche. I just ordered an extra cable and installed one in each vehicle so that I move the head unit back and forth.

So far, I've just held it in place with velcro. Not a very secure mount for sure. I mount it just above the headlight switch - easy to read.

I'd like to know how/where others have mounted their scanguage II. I'll try to post a photo in a little while.

I'm quite happy.