1. If you have an original or replacement honeycomb radiator performing a flush / reverse flush is a good start.

2. Pull off the side cover plate on the drivers side of the block. The back of the block and the areas on the other side of the outside of the cylinder walls accumulate rust and debris and need pressurized water to clean them out properly. Get some stiff wire and form it so you can snake it behind the cylinder walls to encourage the accumulated material to dislodge.

3. Check the block side plate cover you removed for blockage and rust thru holes in the distribution plate that is on the inside. You should have a plate on the inside of the side cover plate that has multiple holes in it, each about 5/8" dia. These holes supply water from the water pump and direct it to the spaces between the cylinder walls and thru to the valve area. If this distribution plate is missing or has rusted out, the block is not going to be cooled properly.

I've cleaned out significant amounts of "sludge" in the back of these blocks by removing the side plate cover, even after performing reverse flushing. Reverse flushing will not generate enough flow to properly clean out the insides of the block. Worse, just reverse flushing loosens up material that ends up, you guessed it, in the passages of that nice clean reverse flushed radiator you just finished.

4. The following links show similar type distribution plates, different make and years from your car, but it will give you an idea of what to expect.

https://forums.aaca.org/topic/336684-plating-a-water-jacket/?tab=comments#comment-1961112

https://forums.aaca.org/topic/362237-water-jacket-advice-and-block-opinions-sought-31-auburn/

5. I had an overheating issue on the same year /model as your car. Drove me crazy until I started looking closer at the Detroit Lubricator carburetor. My issue was running hot under intermediate to higher load. Under light load temp. would drop right down, speed didn't make much of a difference. The DL carburetors have a tendency to run lean if they are not set up properly or have worn parts. My issue was a lean mixture under intermediate to higher loads.

6. Other things to check, if the above doesn't help. Remove the water pump and use some clay to measure the gap between the pump impeller and the back of the block. To large of a gap and the water pump capacity will be reduced. Radiator hoses soft and collapsing, due to pump suction, and restricting flow. Check for correct ignition timing, retarded timing will cause overheating. Fan belt should be tight, loose belts will decrease pump flow.

Some other common cause of overheating:

https://www.rootesparts.com/id201.htm

7. A leaky water pump packing can sometimes allow air to get sucked in. I've had good results with graphite or teflon braided pump packing material, readily available from McMaster.

https://www.mcmaster.com/products/pump-packing/

https://www.mcmaster.com/products/pump-packing/oil-and-water-resistant-packing-seals/

8. A leaking head gasket or combustion gases leaking into the coolant can also cause overheating. Harbor Freight / Amazon / Auto Zone, etc. carry these. Easy to use and will detect a combustion leak.
https://www.harborfreight.com/combustion-leak-detector-64814.html

I usually use the ring manufacturers specifications. If these are not available, Mahle, Hastings, and Summit offer some good info.

In addition to gap, placement of the gap is important also.

https://www.us.mahle.com/media/usa/motorsports/2022-ring-minimums-&-instructions-2.pdf

https://hastingspistonrings.com/wp-content/uploads/2023/05/HASTINGS-PERFORMANCE-CATALOG-1.pdf

https://static.summitracing.com/global/images/instructions/sum-133-m139-00.pdf

Misc. new mfg. Packard parts / services:

https://www.gatsbyautoworx.com/shop

Courtesy of the Studebaker Golden Hawk Register

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1955-56 Packard Oil Pump Gear Set NOS

https://www.ebay.com/itm/374724090942

Packard pedal car, at the Museum of American Speed, Lincoln, Nebraska

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Sold for $20,250 on 4/16/22

https://bringatrailer.com/listing/1933-packard-twelve-roadster/

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Looks like galvanic corrosion. If you look closely it appears to be around the steel pan bolts and aluminum crankcase threads.

Galvanic corrosion is typically caused when two dissimilar metals are improperly coupled together in a corrosive environment.

Galvanic corrosion is caused by an electrochemical reaction between different classifications of metals rubbing against each other in wet or grimy conditions. This type of corrosion commonly occurs between aluminum and cast iron; copper and steel; and stainless steel and aluminum.

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I've used Crest toothpaste to successfully clean up scratched / hazed over plastic.

https://www.youtube.com/watch?v=rXHTXdlWw1w

Part's stores such as Autozone carry a product that works well also.

Meguiar's PlastX

On the 120 Deluxe, in the factory literature "Steering pillar tube nickle plated at upper end".

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