___ LED Upgrade ___
As for the mirror lights, some 2008 and newer have factory installed LED's.
If your truck is not equiped and you decide to change to LED type, the mirror glass must first be removed in order to access the lamp assembly and bulb. '08 and up style mirrors CANNOT be removed from the outside, you will break the tabs on the light housing.
Interior light upgrade - I changed out the factory 194's 'incandescent bulb' on the interior/map light on my '08 F250 with an LED flat panel style replacement. This lights up the cab in hyper bright, much more light than converting to single LED.