I spent 5 years in CO with the Air Force. Owned three great 64-66 GM's while there. But if you think CO is loaded with them, try Texas, Kansas, Wyoming, Nebraska and Montana. Only thing is you might have to fight the ranchers for them that are still using them. Growing up in Montana we had a 48, 66 and a 72 Chevy. All of which we used until the late 80's when we left.
