Dude you'd be much faster and more consistent with a powerglide.
They take allot less Hp to turn than a T400 plus if it's built right it will be more bullet proof than a T400.
I ran a T400 in my bbc nova for almost 8 years, finally made the change to powerglide and it made a profound difference in my et's being much more consistent ( one shift, verses 2 ) plus the car picked up about 2 tenths and hell I even slept at better knowing it was easier on the motor....lol
JMO
>< Cp