I'm very happy with my set of 3.73s running behind a 4 speed small block (approx 300hp) in a 69 Camaro. I tach about 3,000 at 60mph on the highway, and it gets out of the hole very nicely too.

My Chevelle will have a 450hp big block 454 with a TH400 trans behind it. I have 3.36s for it.
I'm thinking the car will have plenty of launch just from the motor and trans alone, and I might be okay with these gears.
I don't have any experience with an automatic with that much torque so any opionions would be appreciated.
Thanks.

Those gears should be perfect for that combibation. With tons of torque you don't need the gear advantage. I have 3.55s behind my solid cammed 427 and they are perfect.

Daniel