Torque convertor and detonation

What is a decent TQ you recommend for a street car to romp around? Should I look for a used one, or is it something I need to buy new from summit or Jegs? I don't know much about TQ's.
Any 6000 series or 9100 and down series, pre electronic compensator are good.
Plenty of guides to tuning. Need to fix the primary well seal with JB Weld Marine.

Or you can get the 750 street demon with composite fuel bowl.
Your car is way under carbed.