ZL-1 Cobra If you are running a 480 merlin motor, Unless you are running a t-56 viper trans you are way past the power and torque limits. Your richmond trans is good for 450hp and 450 torque rated. I have run one and for normal driving it will hold up OK. You might want to look at the new Richmond 5-spd super street. The torque and HP ratings are 600 for both. It's a 4 spd with and overdrive. You can stay with your 3.31 gears in the rearend of the car. Try and get a low first gear the 2.87 is real good for moving. With the 6 spd I had a 3.25 first gear and never used it on my 6 spd. This gear works good with a 3.08 that I have in my 79TA. If you are serious about a strong trans and doing any kind of racing, a 5 spd G-Force is the way to go. 1,000 HP and torque. It's not cheap but the last trans you will buy. The only down side is 5th gear is 1-1. This will limit your top speed. I now use this one with a custom gear setup and it works. It's the same size as the richmond 5 spd. If you are running the 6 spd the trans mount is 1" farther back. G-Force has some kits for more strenght in some tranmissions, I know T-56 and the 5 spd richmond. Not sure about 6 spds yet. Down the road I may try the T-56 trans I have in my cobra with the new gears and main shafts and have it blue printed. I have replaced a bunch of T-56 trans from GTO's and Trans Ams. They don't hold up under hard abuse or high HP. One car has a turbo kit from STS in it. Trans has broken twice. He's done with the warrenty and getting a G-force T-56. This will solve the problems. Side note not sure how hot your trans fluid gets but if it starts to get stiff in shifting you will need to change fluids to a full
synthetic and drop the weight numbers to a thinner
oil.
Amsoil has the higher boiling point that the others. Rick L.