I think there were some standard-belt engines made after the switch to center-bolt valve covers, but I'm not sure. It is possible that someone swapped the serpentine-belt equipment out. After messing with one vehicle with a serpentine system (my dad's '88 pickup), I love them! It takes a bit of getting used to, and stringing the belt everywhere is a pain, but once it is in place, all you have to do is drop the tensioner down and drive away. Much easier than trying to get the tension right on multi-belt systems.
