I think it's pretty interesting that you found both of those in the Dakotas. My 61 K10 was also from that area. I bought it from the Rapid City antique car dealer and had it shipped back here to New England. Mine was made in the Janesville plant. I'm curious if yours were as well. Mine looked about like yours when I started in the late 90's. Here it is now.
http://rides.webshots.com/photo/2578304020054213402wSjlLJ
http://rides.webshots.com/photo/1305082520054213402lplyLI