Good information in this thread! I did the F14 1683 beacon bulb replacements with "direct replacement" LED bulbs from cointaker:

http://cointaker.com/products/1683 ($3.89 each)

Just plug them in and they work just fine. These are only white or warm white. They light up the beacons just fine with the "white" ones and brighter than the original 1683s, but (as Grumpy is implying) the color bulbs would be more brilliant with the matching blue and red bulbs in those beacons. I'm content. In another week or so I'll be posting a video of it (and other things) and you can check these direct replacement LEDs out. Watch for it ...

Check out the end of the video in the following link for what the "direct replacement" LEDs look like for the 1683's in the beacons on the F14. Go to about the 48 minute mark for a few light shows in dim light.