After lots of research in the shop manual I have determined that the engine in my 1951 is an early 1949. The fact that both water pumps and generator run off one belt from the inner pulley and the fan runs off the outer pulley gave me the clue. Whoever made the switch years ago did stay with a 1951 intake manifold with side-draft carb but with a manifold-mounted automatic choke. According to the shop manual that choke was only fitted to 1951s with Merc-O-Matic and my car has the 3-speed with overdrive. 1949-51 Lincoln and Mercurys all use the same thermostat so I can now move ahead. My understanding is that an 8BA engine is Mercury and not Ford. If anyone with a 1949 can confirm this that would be helpful.