When dealing with overheating, boil-over issues, you have to take in the whole picture. The thermostat is only part of the picture. The waterpump is another critical factor. The waterpump in these Hudson Stepdown sixes have a critical spacing between the impeller and the backplate of about 0.009" to 0.19" to ensure the pump can pressurize the block sufficiently to raise the boiling point of the coolant so that vapor bubbles do not form on the surfaces in the water jackets and act as insulators. The problem with these waterpumps is that when they are rebuilt, the person rebuilding them does not follow the factory setting of the impeller being 0.007-0.017" proud of, or projecting outside of the pump casting, so that when a 1/32" (0.031") gasket is used between the pump casting and the backplate, the clearance between the impeller and back plate is around the aforementioned 0.009"-0.019". This is due to the gasket compressing down to about 0.026" when the mounting bolts are torque down to 20-30 ft/ lbs. I have seen these pumps when the person rebuilding them had set the impeller 0.017" inside the casting, resulting in a large gap between the impeller and backing plate, which allows coolant on the high pressure side of pump to cross over to the low pressure side, dropping the pump pressure or head dramatically.
Another critical player in the cooling system is the brass water distribution tube in the block. This brass tube is inserted into the block behind the water pump, and it's job is to even out the flow and pressure from front to back of the block, as well as to direct a cooling stream of water under the exhaust valve seats. In some cases after a rebuild, this brass tube is entirely missing or mangled. In other cases the coolant holes in the brass tube are plugged up with rust scale and sludge.
Other than the cooling system itself, contributing factors to overheating are late (retarded) ignition timing, excessively lean mixtures due to clogged jets in carburetor, or vacuum leaks, excessive exhaust back pressure, heat riser valve stuck closed, etc. Hopefully this info can help you alleviate your hot running issues satisfactorily. Is this a freshly rebuilt engine?

The radiator, is it recored or new? If not was it tested for flow? Are you using the metal elbow and two short hoses for the lower hose?

Thank you for all the helpful tips. Unfortunately, I do not know if the engine was rebuilt before I got the car some 20 years ago, but I suspect not. It currently has 90,000 original miles, and I can tell you what I have done to date, to try and resolve this heating problem. 1) First I used a heat gage to determine whether there were any hot spots in the radiator, and also to check out the temperature gage itself. Then I pulled the rad and had it boiled out and recored. I flushed out the entire coolant system as best as I could, and have also checked the timing, and have had both carbs rebuilt. Finally, I also built a shroud for the fan. However, I have NOT had the water pump off and have always assumed the old adage of: "If it ain't broke, then don't fix it". But maybe that is something that I should reconsider in light of the information recently given to me. I also was not aware of the brass tube, behind the water pump, which could obviously be plugged. If I take the water pump off, how big a job is it to get the brass tube out (if it still even has one)? Again, thank you for all the great tips. ken

The rad is recored, and I assume that it was tested for flow by the rad shop, or at least I was told that it was 'good to go'. I am using the metal elbow and two short hoses for the bottom hose ---- is that good or bad. Thank you once again. ken

Another thing that can cause overheating is if there is any exhaust gas getting into the coolant via bad head gasket, cracked valve seats, etc. Have you had the cooling system tested for exhaust gas getting into it? Has the coolant blown out the overflow tube of radiator on a consistent basis after driving the car? was the coolant foamy appearing, like the foam on the top of a beer? If so, it could very likely be a head gasket leak or valve seat crack.
Getting the brass tube out will require the radiator and probably the grill to to be removed first as it is about 28 inches long. Some come out without too much coaxing, some come out fighting you, some come out in bits and pieces.....

Is the head iron or aluminum? Aluminum heads give the most gasket sealing problems.

Again, thank you for all the leads.. Taking that brass tube out does NOT sound like much fun, nor am I anxious to remove both the rad and grill again. But I will keep and eye on things and see if the addition of the fan and new thermostat help. The head is NOT aluminum on my particular motor. However, I will try and determine if I might also have a gasket leak. You guys are the BEST! ken

If you did not block off the bypass when you changed out the thermostat you are not getting optimum coolant flow through the radiator.
The SUGGESTIONS FOR IMPROVING YOUR ENGINE COOLING link on Ken Cates' webpage has a good walkdown of this and other cooling system improvements: [url= https://hudsonrestoration1948-54.com/CoolingSystem.htm ]https://hudsonrestoration1948-54.com/CoolingSystem.htm[/url]

I don't see it mentioned, but one thing to check before you go to all the other trouble, is to check timing. It can make a big difference in temp if the timing is too advanced. I do initial timing with a timing light. I then hook up a vacuum guage to the intake manifold vacuum port and check vacuum range. Once there, I will retard timing a little and check. If it has been too advanced, the starter will have more of an issue turning the motor over for starting. I will turn the distrubutor towards retard (clock wise) a little then check starter turning, and vacuum again to make sure it is in the proper range.
Just did a newly built 232 this way and it dropped temp by 25 degrees.
https://fordsix.com/archive/www.classicinlines.com/Vacuum.html
Ken has a good write up on his site that I have used-
https://hudsonrestoration1948-54.com/How%20to%20time%20a%20Hudson%20engine%20with%20a%20Vacume%20guage.pdf

Sorry.... Kerry I have set up my website to disallow direct linking to the data there... the attachment is what will appear when you go to my website and select Ignition from the maintenance selections. This information appears on that page... Ken Cates

My thanks to Ken Kates. I did attempt to check the timing, but NOT in the format or process that you have suggested, so will definitely do so. I also did not block off the bypass when changing the thermostat, so will reattempt that procedure as well. You guys are the BEST, as I live in a rural area in central British Columbia, Canada, where there are few knowledgeable Hudson owners; I very much rely on H.E.T. advice. Have a great day everyone, and please stay healthy! ken