Get a new door and have it painted at the same time as truck. Leave original door on the truck with new paint job and drive and see how you like it. If you don't, put matching paint door on and make wall art, a garden gate or display it in the back at car shows. There is a chance if you put clear on it, it will react with old paint or you won't like the gloss. Try a little wax on it, not the rub hard kind, use the no rub kind, to see if you like it and it does not rub off the hand lettering. Try on a small corner of door first. Can't view your link.
