[WarrenG]

I went with the TKO600 also. As mentioned above the cost difference was minimal ($150 I think) especially compared with the total cost of the build. I have 3.54 rear gears, 26.5" tires, and the 0.64 OD and that set up works fine for my small block build. Also as mentioned above, I think the 3.27 1st gear in the TKO500 would make 1st almost useless in my car. However, if I had 3.31 (or 3.27 like yours) in the rear, I would opt for the TKO600RR and the 0.82 OD.