As far as manuals go, what's the performance difference between a 5- and 6-speed? I've heard good and bad on both.

 

Difference how? The v6 wouldnt have the torque for the 6spd.

 

And the V8 would tear apart the 5 speed. Also, the six speed has two overdrive gears if I'm not mistaken? Helps with mpg's on the highway.

 

One speed!

5 speed is for the V6.(V6 does not have the torque to 2 overdrives)

6 speed is for a V8.(V8 engine would destroy the 5 speed)

 

as far as a v8 goes the 5th gear is an overdrive gear but you can still pull a little power with it so that is why the 6th gear is needed. in v6 that is not needed since it wont make enough power.

 

Gearing:
T56 - 1st: 2.66, 2nd: 1.78, 3rd: 1.30, 4th: 1.00, 5th: .740, 6th: .500
T-5 - 1st: 3.50, 2nd: 2.14, 3rd: 1.39, 4th: 1.00, 5th: .730
As you can guess, the V6 will perform better with the T-5's lower 1st & 2nd gears.
After that, they're pretty much the same from gears 3-5.
6th on the T56 is a double overdrive, too high for the V6 with it's lower low-end rpm torque to benefit.