I just pulled my shop manual and will try to locate the other grounds. More than likely it is the ones exposed to the elements.
1. there is a ground on the frame near the LH front radiator support. Follow the harness it appears to be close to the body mount by the support.
2. there is a ground for the instrument panel that appears to be on the right upper part of the dash and another on the left upper part of the dash. appears to be the metal dash frame. There is a stud on each side.
3. The major ground i referenced before is the LH frame rail at body mount.
4. Another ground inside behind the trim of the LH "B" pillar.
5. Ground on the LH frame rail near the body mount before the rear leaf spring.
6. Driver's power seat ground under the drivers seat (inside)
7. Ground (regular cab) inside the right rear pillar near the speaker
8. Ground for the fuel sender harness near the tank on the bed mount bracket.
9. A ground in the plenum (where the windsheild wiper motor is) which does tie to the instrument panel harness.
10. Of course you have the major ground to the engine block.
I would start with the ones that attach to the frame rails and then all the other exterior grounds since water, dirt, salt, etc. will deteriorate the ground connection more likely than those inside the vehicle.
Even if it looks good, disassemble wire brush is and reassemble and coat.
Good luck
