I ran my negative cable all the way to the Bellhousing. I also ran a ground strap from the bellhousing to the fireway. Can't think of a better ground than a bellhousing bolt. It's also 6 inches from the starter which is the biggest load in the system. When I researched it, the consensus was that running the cable was the best route. I'd rather ground through a 0-2 gauge high quality cable than 40 year old sheet metal and frame.
More than one way to skin a cat.