As mentioned before, the older Mopar engines are always in demand. Diesel pickup engines are generally worth pulling as well, either whole or to strip for core parts if they're complete.

A horror story related to this subject- Several years ago, a buddy of mine bought and scrapped a Swiss-cheese rusted old Chrysler that had been sitting for many years. He just hauled it in whole, and found out after the fact that what he had was a 1957 Imperial with the original 392 Hemi Needless to say, that engine never made it to the crusher, and he left a lot of $$ for a happy junkyard guy.