['68OrangeSunshine]

I re-edited my last post after you replied, to add a pic of my head. I used brass set screws with allen heads. I have headers. So I replaced the end studs with bolts, as headers need more clamping.
My guess on XAE is that it was an exchanged motor under warranty in the PO's first year.
Some of the senior pundits on this forum have puzzled over that dress number, but it's all lost in the shrouded mists of history by now.