I don't want to rain on your parade, but as far as what battery works best, locations and track conditions are kind of important. Just because a guy had success at one track, does not mean the same formula will work elsewhere. The difference between running outdoors at Aliso Viejo, an indoor carpet track in the mid-west in January, or on rubber mats in your basement is huge. Temperature, surface conditions, track length and even humidity play a part. Don't get to attached to any one idea, because eventually you may be in a real race and things might be different.
I believe the Belleville washer you want to remove from your diff is the outermost one.