According to this sitehttp://www.radiomuseum.org/tubes/tube_7c5.html the 7C5 can be sub'd. No idea if that sub is still available though. Another site says a 7B5 will work as well. The rectifier or also the vibrator can be replaced with a modern solid state retrofit if that were needed.

As others have mentioned, valves are the least of the troubles when getting an old radio operational. The capacitors and anything with degraded insulation must be changed first. After that if a valve is needed, then if NOS & a sub is not available there is always used or possibly Russian.

One thing I have heard but not sure of is a slight difference in frequency standard between US and Europe. Someone with a direct American import can say if that is true and if something has to be adjusted.

I know it's farfetched but kind of wondered if somehow the choke or general airflow was getting sucked closed too abruptly after the drive and slowdown. Maybe the large sudden increase in vacuum was overpowering the thermal spring. Opening the throttle would also open the air flow or choke linkage. I know some earlier engines had throttle dashpots for a similar reason.

Other than the idle circuit don't see what is left and if idle circuit (or choke either for that matter) were bad, then why not happening all the time.

One of the less expensive early AMC factory units but basic hang ons are all about the same.

Differences usually is age and type of blower. Unless a single speed, the older motors with two wires use something with resistors like this or a simple rheostat. 53-4 Packards used the resistor block because of confined control box, 55-6 Packard used rheostat. Stude's with hang ons I have info for, rheostat. Cheap but effective -- downside is heat dissipation - fairly large & resistors have to be in the airflow or in the open.

Later aftermarket units with motors having 4 or 5 wires use same basic multiposition switch but no resistors and feed field coil differently. Less current & no hot resistor to worry about.

As PV8 says, it is a basic circuit but there are some variations. Unsure from your description if you have the blower switch with the resistors attached or if you have an on/off and separate resistor block. Here is a schematic showing separate resistor block. Pick your own colors and wire as shown. If you have the switch with resistors then the blower would connect to the H terminal on that switch instead of resistor block.

If you have a single on/off & speed switch, then one side the thermostat will attach to the C terminal on that switch instead of the separate switch the schematic shows, otherwise the same.

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Thanks for fixing. Works when you go directly to the vendor page instead of thru parts123 sort. A modern replacement in plastic worth looking at for the price difference..

Nice you could find the size so visible. Maybe that one rusted out the last time and was replaced. The paper restoration is interesting. Thankfully the ink wasn't water based. Now if we could just find a reference to that one unknown item.

I think just a gasket cement on one side to hold should be plenty. Make sure the cover is flat around the holes so it gets good equal pressure between--just like the oil pan. Maybe not necessary, but I think I would moisten the cork with oil so it doesn't spin dry on start up. There was also an arbor that fit over the crank to help in centering the cover with use of a feeler ga. I think that was fairly important so the seal was not subject to off center wear. I would at least eyeball to center the crank in opening as much as possible.

That particular tool was made per Packard spec and use but a trans shop should have something that works. There must have been more than one trans with that blind bushing arrangement although maybe not in the same size.

Do you have to pump the gas or just open the throttle to keep it going? Assume standard shift?

You really need proper tools to extract and replace bushings. Some you can make do with home made or other methods but those in converter are going to require something to go behind then expand and grab and pull.

On the bushings in general, you need to be careful you don't scratch, distort or get them started crooked & mess up the seat area they fit into or you've just wasted your money. They are a bit fragile and don't have a lot of tolerance before they leak as bad as the old. Also have a good look at the shaft areas they fit around for any signs of wear. A new busing won't help a worn shaft for very long.

Have a look at service counselor Vol 28 #12 for the tools and proper method of using themhttps://www.packardinfo.com/xoops/html/downloads/SC/SC-VOL28NO12.pdf The service manual also has some instructions on removal/replacement.