they may have many miles on them, but the 6.0 moves around 3/4 and 1 ton pickups plus their loads daily. there is a reason GM never put the aluminum block 6.2 in heavy duty pickups. the 6.0’s were made to be wound up and worked daily. the 4.8 and 5.3 are good motors and i’ve swapped quite a few into other vehicles. i’d much rather have a 4.8/5.3 than comparable dodge/ford offerings until the coyote.