Get a copy of Chef's Book of Formulas, Yields, and Sizes by Arno Schmidt, published by Van Nostrand. I've got the second edition from 1996, but there might be a newer version since then. Also, Macmillan publishes Quantity Food Purchasing, by Lendal H. Kotschevar and Richard Donnelly; again, there's probably a more recent edition that the 4th from 1994.
Both of these have specs for a wide range of produce, meats, fish, dairy, and dry goods.