How are your going to use the truck? Do you plan to use it to haul stuff, or will it be strictly just for display (like the hood and roof?) That will play heavily into what you do with it. Bruce Horkey is the most knowledgeable person out there on bedwood. That's all he's done for at least the last 15 years or so that I've known him, and he's experimented with everything possible to find what's best. Check out his website for some helpful information and ideas.

His site says:
Finish Kit
After much testing, we have put together what we feel are the best finishing materials in a kit form. The kit includes a marine- grade, tung oil-base spar varnish with ultraviolet blockers built in; a special reducer containing naptha; two quality natural bristle brushes; garnet sandpaper; Scotchbrite pad; a tack cloth; and complete instructions.

Bruce Horkey - Finishing for Show Decks

http://www.oldgmctrucks.com