180-200lbs of raw butts is what you need because 50% loss is my rule of thumb. I know many will chime in and say they get 6-% or 65% yield and yes so do I sometimes. My yield averages 55-60% but sometimes you get a case of butts or scenario that will less. At 180lbs with a 60% yield you will have 108lbs of pork allowing you to make 432 1/4lb sandwiches if you get a 50% yield off of that you will have 90lbs of meat and have enough for 360 1/4 sandwiches and an angry customer who has 40 people with no BBQ.
FEC 120, Lang 84, Custom Off Set