According to my Haynes manual, you are at least 50% correct; the cruise control pickup is internal to the speedometer. Haynes doesn't discuss the emission service reminder light and it doesn't show up on the elctrical schematic in the back either. I've got two 83's, one with cruise and the other without. The one with cruise definitly has the extra box and short drive cable. I didn't think the one without cruise had the box and short drive cable so I deducted the cable and box must be for the cruise. I bought one of the 83's new and the other with 10k miles (it was cruise). They are both pushing 300k and I don't recall the service reminder light on either ever coming on. In the mid 80's I had the dealer do work on both so perhaps they reset them or disconnected them. I'll probably stick my head up under the dash on the one without cruise tomorrow to see what's going on. Do all the speedometers have the cruise coil pick-up even if cruise wasn't installed? Thanks for the enlightment. jp