There's one North of Willmar called Rohner's that has a lot of older parts. They used to let you go through the yard and find stuff, but that changed a few years ago.
There's one by New London called Windy Hill. They still let you walk through the yard. Was there looking for steel rims for a Dart. Found a couple of Slicks (61-66 f100) that had a few good parts on them. They cleaned up a lot of the older "junk" a couple of years ago. Didn't see too many 73-79 Ford trucks.