I figure chicken at a 1/4 per guest if it is the single meat, that would mean 75 chickens. Cut into thigh, drumstick, wing, half breast. Wings don't count as a piece.
For two meat, figure 30 to 35 chickens, 4 breast pieces, drumsticks, thighs and wings, one per guest, wings don't count as a piece
If you are feeding that many people and doing chopped chicken, I would go with boneless breast and thighs. The price is better on them, they are easier to cook and you will have less waste. Depending on where you get your meat will determine how many cases you get. I get 40# boxes of each and they will yield about 110 5 oz portions from each box. I have been cooking and cutting up as needed.