Heckers, and its sister flour, Ceresota, are regional brands of a high quality unbleached all-purpose flour. See http://www.ceresota.com/about.htm
. Member buzz is the expert on the Ceresota flour, which he uses for just about all his pizza doughs, and especially his deep-dish pizza doughs. It is quite possible that the two flours are now the same. I believe also that the two flours are slightly lower in protein content than the King Arthur brand of all-purpose flour.
The larger sized bags of Heckers a-p flour are sold at chefswarehouse, at http://www.chefswarehouse.com/Catalog/DisplayDetail.aspx?prd_id=GF249