There are LED replacement "bulbs" that have the same bayonet base as the
1157 stop/tail lamp bulbs and the 1156 back up lamp bulbs.
Unfortunately the are intended to go in where the original bulbs point
straight back instead of crossways, so as the LEDs are very directional,
even the wide angle ones, the reflected light going out back is
diminished.
You might put the truck tail light unit in behind the original fixture so
that the original lens is still used. Then it will look original but
still be a low current draw LED tail light.
Having the original lens in place will reduce the light output but these
super bright LEDs are so bright that your taillights will still be amply
bright. Or you might cut the LED taillight unit's lens away if it's made
so it can be removed without damaging the LED array.
Al