You know, sometimes I wonder how I became an old man. I was measuring from the front of the bolt head to the center of the retaining pin hole. The J bolt head is about 80k thicker than the newer head. I measured from the back of the head to center of retaining pin hole, it is right on the money. So a SA bolt head will work. I wish I could blame it on the booze, but I haven't had a drink in 15 years! Oh well, now the search for a .308 bolt head begins. Thanks for your help. Jogged my brain loose, got me to thinking.....