If you ever watched "Roadkill" garage or Roadworthy Rescues" You can google them, as they no longer make new episodes, but just about any of their episodes have some old bone yards in the Mid west to Rocky Mtn regions.
I stopped by 4,5,6 Chevy trucks in KC. Kansas/Nebraska have a lot as well. You'll be rubber necking!!
We did RT 66 it's worth the drive in some spots for sure.