Richard, FYI, Walt Mordenti sells a fine bypass kit to use if you wish to use a modern thermostat.

The Hudson thermostat had especial rubber around the top that closed off the by pass hole when opened. Without this special rubber the by pass will always remain open and that steals water from the radiator. You can not buy this special rubber ring as it was sold only with the thermostat. There is no part number for this item. With todays gas you only want your engine to run with a 160 degree thermostat. Get caught in traffic on a hot day and you will be in trouble. My set up warms the heater right away as I modify the thermostat and the block off plate. Enough said, Walt.