If you would like something good on the street and the strip look at a switch pitch torque converter , like what buick or caddy used in the 60's you can really tell the difference when it kicks in.
I don't know how familiar you are with the switch pitch theory so just in case you don't know
.The stators change angle as you accelerate creating more torque throughout your power band. You can hook it up to your th-400 or th-350 There are companies that sell everything you would need or if you can find a good junk yard you might find one.