TKO 500 or 600?

[usc2001gc]

Well, it looks like my deal on a T-56 trans for my 71 chevelle fail thru. So I guess I'll be putting a tko 500 or 600 in my car. The question is, which gear ratio (500 or 600) would be best for my combination. I'll be running a mild 402 BB, with a 2.73 rear (if the code is correct on my axle housing....need to pull the cover and check the actual gears before I order the trans.) I'm leaning toward the tko-500, due to it's 3.27 first gear ratio. I'll probably leave the 2.73 in the rear and maybe enjoy some fair gas milage.

Also, I was considering a hydraulic TOB, does anybody make one for the TKO that's more affordable than the McLeod (~$375.00)? Or should I stick with a mechanical system.