Well, I was looking through some of the older posts on the clinometers that folks have decided to use.

I opted for the Reiker Instrument Co. Clinometer, that has a glass tube filled with a dampening fluid, and a metal ball.
They were made for the marine industry and are very duable, yet precise for measuring.
Here is the link...
http://www.riekerinc.com/M-Inclinometer/2055e.htm

I realized that the any place other than a manufactured trail is not going to have any info on the slope of the terrain you will be driving on.
I ordered two, so one can be used for breakover angle, and one for approach & departure slope.
I will need to play around with mounting ideas, but I am usually pretty good at coming up with solutions.