I'd guess the majority of ghost/historic/mining towns are accessible by most 2wd vehicles. However, "suggestions" would be difficult until you pick a travel route, as they're quite numerous.
You have at least a couple of options. You can pick a route, then go this home page and use the drop-down menu under "United States" to scroll thru some sites you'd like to see on the way. Or you can go to the drop-down menu first, make a list of some of the towns (state by state) you'd like to see, and plan yer route from that.