Speedometer cable(s) for 85 D100

[dosperros]

Just spoke with my mechanic. He purchased a speedometer cable for my D100 but discovered it is the wrong one. If the truck came with cruise control, the speedometer requires 2 separate "cables" for it to work. If I choose not to use cruise control, can the single speedo cable work? If not, does anyone know of a vendor or junkyard that may have to speedo setup for cruise control?
Also, is there a gps speedometer that will take the place of my stock speedometer? I can take my time finding the cables I need. I can always track my speed with my phone. Dodge owners never say die!