If your truck is a sunny day garage queen, you can use any kind of hard shell glossy/satin finish and it will last a long time before you have to strip it and redo.
But if you are actually going to use it like a truck, any coating from varnish to epoxy, is only good till it gets scratched or chipped and then it's just a matter of time till that grows into a mess.
Pick a wood that's the color you want so you don't have to worry about stain and finish the wood with Thompson's weather seal (not the water base). 2 coats all sides, extra on the ends.
Doesn't matter if it gets scratched, cut or dinged, wash the dirt off and recoat the top every year.
Works great on quarter sawn oak, Douglas fir, heart pine, etc
If you want it dark, I did the '48 2 ton (12 ft bed) in black walnut and it looks great. Correct amount of gloss (or lack of it), color and carries real loads.
