A lot depends on the torque curve and what you want to do with the car. A custom full on race converter could run a 9.5 inch core, stalled more for max et, and be loose, like 6000 stall. A car mainly driven on the street where you want a more responsive setup, might be on an 11 inch core and stall 3600. Your info provided to a good converter builder will provide him with info to build what will suit you.