I have a small block with lots of low end torque with 3:55 rear gears and 26" tires. I went with the 600 because of the first gear. With the TKO the 3.27 first gear was useless. The 500 has the same first gear.
Now I cruise at 70 mph (2000 rpms) and I have a first gear I can use.
You need to do the math and see what your cruise rpms will be at 40, 60, 70, 80. You can change tires size or rear end ratio to optimize your cruising.
Some motor will not cruise below 2000 rpms mainly because of cam profile.
Some are just tuning problems that you can easily correct.
IMHO you don't need the 600 because of the torque, tires are the weak point on a Cobra. But the first gear and the 5th gear ratio are what your looking at.
The clutch is different on the 500 and 600.
Who ever you buy the trannie from also buy the clutch to match.
I have bought 5 or 6 trannies from D&D and will buy my next one from them. Best price, great service and they stand behind their products.
One of my buddies bought a trannie from them. It had a problem and Tremec got involved but D&D shipped him a new trannie and let him keep the old one that Tremec had repaired. Not bad customer service. That happens this past summer.
Welcome to D&D Performance - The 5 & 6 Speed Experts!
Dwight
happy cruizin