8 to 10 hrs labor to change '225' head gasket ?????

I don't think 8-10 hours is unreasonable. It is not rocket science, but does take some time. OP stated swaping manifolds, and replacing bolts, not just changing the head gasket. Chances are at least one broken bolt if not more, cleaning parts, including rocker arms and shaft, then adjusting valves after putting back together. While it is off it is always a good idea to change the valve seals, also (and that takes time).

On a clean engine, with manifolds (not headers), I can change a head gasket in about three hours, as it is not necessary to take the manifolds off the head, or clean the rocker assy, just scrape the head gasket and reassemble.