Hello Richard,
We use the RV specific model from Garmin.
http://www.rvupgradestore.com/Garmin-GPS-p/22-1590.htm
Ours included Lifetime Map Updates. We like it so far.
Stan
This model just was released and is getting good reviews from lots of people. If you don't want to spend quite as much, we've been using a Garmin 465T for over 2 years with reasonable success. The 465T is a "trucker" GPS that keeps you out of trouble by knowing your height, weight and length. It's principal drawback is that it doesn't know that RVs can drive on truck-restricted roads in many situations. As a result you sometimes take a more circuitous route than you could have used. Other than that, I think the 465T is a good unit for ~half the price.
There are a bunch of other features on the 760LMT that you may like, such as RV-related points of interest, and the ability to link the GPS to a smart phone (for a price), but pretty much all of those can be accessed directly from my smartphone so I have no need to incorporate them in my GPS. I want my GPS to be the best it can be in doing the job I bought it for; I have no need for it to try to replace or duplicate my phone's functions. JMO
All that having been said, if I didn't already own the 465T and an older 765, I'd be writing out an order for a 760LMT. Does anyone want to buy a 465 or 765 in good condition?