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I am a little confused/curious on James' comments re 38/39's not having cylinder head T-stats, 'just shutter stats'. My '39 Six (1700) has both. My understanding was the rad thermostat's sole purpose was to activate the grill shutters and had nothing to do with controlling the flow of coolant through the head and block - is this incorrect?? The head thermostat fits up in the rad-to-head housing and has a stainless sleeve to retain it in place. It is 160 degree and my take was THAT was what controlled engine operating temp. Do I need a refresher course on how Packard's cooling systems function???

Just take note that you can also control engine temperature in liquid-cooled engines by controlling air flow to the radiator, no air thru the radiator = essentially no cooling.
That was a common method until the early to mid thirties and is still used on some stationary heavy equipment and highway trucks. My 1934 Eight has a shutter thermostat and no provision for a cylinder head thermostat. The growing popularity of higher boiling antifreeze (glycol replacing methanol) and hot water heaters replacing older type manifold heaters was a driving force in the change.

Bottom line, you could have one or the other, or both. Ultimately controlling coolant flow turned out to be more effective than controling air flow.

Ahhh, I see... thanks for the explanation. Is it possible the head T-stat in my car is an 'add-on'??? The reason I ask, is most thermostats I have ever dealt with, sit in a recess in the head or coolant intake lower housing and the rad-hose-bib casting fits over them and locks them down. I have never seen a setup where the thermostat actually fits up inside the hose spout. Thought maybe it was an 'attempt' at an after-market addition of a coolant t-stat??

I don't know how yours should be configured, you might look for an illustration in the shop manual or parts list. However in some later engines Packard did mount the thermostat in the top of the cylinder head hose gooseneck and used several methods (sleeve or wire clip) to secure it in that position.