This is what I have been wondering when
@Apparition talks of overheating. I believe his F150 had the turbo.
My GM 1500 towed my current LJ just fine on a Uhaul trailer for a long haul but no mountains were involved. I know towing a load like that routinely is better off with a 3/4 or larger truck but I am very happy with the performance of my 1500 for the infrequent trip.