on later trucks the factory put a ground strap [the flat braided type] from a starter bolt to a threaded hole on the toeboard part of the floor,
like such, red X - for the bed I added a heavy wire from the frame to a hole I drilled on the back cross-sill, which is well bolted to the bed sides - use a good toothed star washer under both ends of it to dig in to the metal, same as the factory did on that cab ground - the frame will usually get a good ground from cab mounts, but it doesn't hurt to add one from a starter bolt
