Oh, yeah ... speedo cable ...
Lokar is a good place to start. There is a place that makes cables for older vehicles, such as the cables for old pushbutton A727 transmissions, but I can't seem to find the link for their site.
Assuming you have a Class C, a B100/200/300 van cable should fit. Class A's often have different cables due to difference in cab manufacture but Class C's have the same cab as vans, with the same distance between the instrument cluster and tranny speedo gear.
Unless you really, really want cruise control, do what Leeann suggests and go with a standard non-cruise cable. (Older cruise controls tend to be problematic due to being mechanical mechanisms rather than the newer computer controlled electronic systems ... I usually chuck cruise controls on older vehicles.)
