With 8"s of total lift , oversize tires ? , driving in steep snow covered roads ? and the trucks center of gravity so high and a short bed wheel base with the slowed suspension response I wouldn't push it over 40 mph . Guard rails don't care if it's 4wd they still bite .I wouldn't want to be the guy coming the other way seeing you running 60 in my lane on a corner on a snow covered road . Conditions determine SAFE speed NOT EQUIPMENT .
