How about using 2-guage wires? I've seen it done here:
http://www.cardomain.com/id/linnfreak

Anyways, how about:
1. Upgrading all "wimpy" ground wires to 2-guage, including the "big 3"
2. Add additional ground wires that run to the negative terminal of the battery (possibly using a distribution block)
3. Run a ground wire from the alternator's metal body to either the chassis, or the negative terminal post.
4. smearing all ground points with dielectric grease to prevent corrosion.

All wires would use good quality connectors and heat-shrink.

sound good?