[1969 GMC]

I know that cheap little stick on digital clocks are a popular choice for our trucks, because most lacked a dealership installed analog clock. There was one on my truck's dash when I bought it, but it was dead. New battery was $7. Another El Cheapo clock was $6. Dunno how that works. But I instead opted for the Bell Inside/Outside Thermometer - Clock, $10 at Wal-Mart (located in the car section). It has a wired sensor that runs outside the weatherstripping and will give fairly accurate outside reads. The inside sensor is built into the main unit. It attaches to the dash or wherever with two velcro squares. It also has a nice backlight, so you don't have to turn on the ol dome light to see what time it is after dark. And for those who like gadgets, this is a must.
The unit works great but only after a minor modification. When I first connected it, it would keep turning off and resetting the clock. I thought the included battery (a triple-A, so it won't cost $7 to replace) was dead, but no such luck. It turns out the spring contacting one of the battery terminals wasn't long enough...I just had to stretch it and now its fine. Overall, I am happy with it, and I recommend to anyone looking for a cheap digi clock for their truck.