Best RV GPS for USA, Can and MEX w/ Lifetime Maps

Been a while since I posted. I have bought a newer 2008 Foretravel 42 foot motorhome w/ a tag axel and 400 HP Cummings. I am looking for the best North America (including Mexico maps) GPS. Definitely want a 6 inch or larger screen. More concerned about underpasses, bridges, and commercial routes for larger RV's. Any suggestions would be appreciated. Will be crossing at Anzalduas Bridge and headed to our home in Querétaro for the Christmas Holidays, from there on to Valles, San Luis Potosi and return sometime in early January. Might be interested in Caravan if it is possible. I will be overnighting in Matehuala at the Las Palmas Hotel.

Thanks,
Robt65
Mission Texas
& San Juan del Rio, Querétaro