Good going Larry. I know well the feeling of bringing life back to a dead engine. Great feeling, isn't it.
I had a similar start-up experience on my last head replacement, sputtering, coughing and smoke, which cleared up as I gained speed. Found that I hadn't gotten the air box completely sealed, and the change in pressure was affecting low RPM performance. Once tightened down it ran fine.
Keep us posted on the repair for the first 500 miles or so (should only be a day or two for you
73 280 SEL 4.5