Unless you're trying to build a 100% correct show truck, it makes more sense to run the battery ground cable to the engine block or one of the bellhousing bolts. The starter is the heaviest current draw in the electrical system, and a heavy-cable ground as close to the starter housing as possible assures that it will have the lowest resistance current path available. A #8 or larger ground conductor from the frame and/or body to the engine, and another one from the frame to the bed will eliminate a lot of electrical gremlins before they get to be a hassle.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!