Not sure what the light bar is doing ( warning light bar or if you mean recon line of fire type light bar ), but it would be better to wire is to the trailer tow adapter. This is a separate fused from the truck's stop / turn lamps and the parking lamps are on a separate fused circuit via a relay.
If you still want to wire it directly to the truck's stop/turn/tail lamps :
Stop / Turn :
Parking lamp wire is the brown wire in the tail lamp.
Reversing lamps :