The best guages are oil filled and should not be disturbed by the "BUMPS & RATTLES". This guage on EBAY is quality.
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=2413126233&category=67 73
I own one and it works very well. The most important thing to remember on a a side slope is don't be afraid at any moment to turn down hill if you feel you are over the limit of incline performance. Although turning into the fall or turning down hill seems unnatural for some it is often times the only way to save yourself from a role.