[Steve1968LS2]

Since I am sitting here waiting for a phone call..

TK0600 -- 5 speed with the 5th gear being overdrive.

K56 -- 6 speed with the 5th and 6th gears being overdive (double overdrive)

The main reason the T56 came to be was because car companies needed to get better milage to meet CAFE standards. The double overdrive (6th gear being .50) allowed high performance cars like the C5 and 4th gen f-bodies to get up to 27mpg on the highway. If you get a T56 get the 6th gear in something like .68 since the .50 is almost useless.

The TKo600 is exactly the same as the TKo500 with the exception of a slight difference in ratio and one part (can't remember which one) that makes it technically a wee-bit stronger than the TKO500. Most people get confused and think the TKO500 is a five speed and the TKO600 is a six speed when in truth they are both almost identicle.

If you are not making huge power and don't require the double overdrive then I would go with the TKO500 and save some cash. If you can afford the difference then upgrade to the TKO600. I would reccomend Classic-Chevy-5-Speed for the TKO stuff and if you decide you want the T56 I would suggest American Touring Specialties (ATS).

Oh, some feel that the T56 is bit more smooth in its shifting.