i have a 64 3/4 ton with which i pull a 35foot fifth wheel trailer 1973 self contained recently i left la california for seattle washington the truck is origional 4 speed with a old 350 motor the trailer weihged about 15000 pounds 1 went 1200 miles with no problems exceopt for using two gallons of oil it leaked but didnt smoke at all we went slow on some hills but we made it on 275 dollars and old tires chevy trucks are the best made! nobody could beleive their eyes when they saw us coming down the road! we were the oldest truck on the highway! it was cool id do it again! smile