I have a 1994 F-150, and put on new headlights, cab lights, and plan on getting an LED 3rd brake light soon. After that I might see about some tailgate running lights, but I'm not sure how much amps I'm using. Is there any way I can check how much I am currently using?

 

Most full size led bars draw 250w realistically. Say 300 for error. 55w each headlight = 110w. 65w for high output Hella bulbs or 130w for the pair. Average 100w for all parking brake and running lights. Minimum 60a alternator for a stripped f150. Add 25 - 30a to the 60a minimum and your looking at a 90a alt to get you by. Your not going to stop there. Go for a 130a and you should be fine with any future stereo amp upgrade or extra lighting.