Torque converter size

Hi guys,
My 72 340 duster has a stock torque converter . Here's a little info of my engine. Stock heads, purple shaft cam, 10 to 1 compression,and stock manifold w/holley carb. It dosent like to idle in gear so I need to upgrade my T/C. I built this engine about 20 years ago(dosen't have any miles on it). I've been using it more and drivability is becoming a pain.
My question is a 2000 to 2400 stall converter a good choice? How many inch? Is a stock converter 12 or 13".
Thanks Mike