Generally, a poor ground will be noticed when the throttle cable begins to glow red hot. If the starter is working fine, then the chance for a poor ground is somewhat small. You might want to clean both ends of the ground cable at the battery, and both ends of the chassis to tranny ground cable. You need to look somewhere else. Try the diagnostic approach in the BGB.
this may or may not relate...but have you guys noticed when you turn your steering wheels while you stand in one place or press any of the buttons and you look at your gauge cluster it like DIMS?????...could bad grounds cause that or is it the ALTERNATOR or BATTERY?