I put brand new 50 amp fuses in and everyone I've put in keeps blowing also the tail light doesn't work either on the driverside

FIRST of all you check all the items on the fuse that blows then remove all the fuses or wires to that item,i dident think the tail lights were 50 amp but still remove the plug from the rear lights and trace them to wards the front ,it sounds like a wire harness is trapped and shorten out about where the door shuts .where the tail gate closes.something under the floor .or under the body on chassis,but when you check all that works like nothing on the left of cab then thats where you start looking .or a wire hanging on the side of the engine ,but dont put in any more fuses untill you have checked out all possible wires either trapped or not .
Keep looking and you will find it AND only use the amp fuses the book says nothing bigger as a dead short wont only blow it can cause a FIRE.
lET ME KNOW HOW YOU GET ON it will take you a few hrs ....goodluck.
Ron