TodFitch

Curious about the reason to change polarity if keeping 6v. I don’t see an advantage.

It isn't really a sending unit but rather an ether filled bulb and the "wire" going to the dash is actually a small tube. The dash unit is the same basic construction as a pressure gauge. The way it works is the ether evaporates as the engine gets warm and the pressure from the vapor moves the needle on the dash. The bulb, tube and dash unit are all sealed and can not be replaced separately. Since you mention that the dash unit is reading halfway, it is damaged or at least out of adjustment. Because of this your best bet is likely to look on eBay or equivalent places for the complete setup. But if that is not practicable, you can graft a new bulb and tube from a universal aftermarket "mechanical" temperature gauge on to your factory head unit. You might be able to adjust your factory head unit (bend the linkage between the Bourdon tube and the needle, not the Bourdon tube itself to adjust). I have a write up on grafting a new bulb onto a factory head unit on my website. It has been a long while since I last did it so I don't know current prices, etc. Or even, in your case, if the same type of after market temperature gauges are available in England. The aftermarket units available in the US come with an assortment of gland nuts one of which should work in your engine's head. I haven't figured out all the ins and outs of the new fangled anti-freeze solutions. I still go with old fashioned green ethylene glycol.

I got a 6v+ to 12v- converter/inverter that I located under my dash. It feeds a 12v style accessory outlet for charging my phone and it also powers my dashcam. The specifications on it indicate that it could power a modest (low power) radio or CD player. So if your stereo power needs are low (less than about 40 watts) that is a possible way to go. I would not try to power a 12v motor from it no matter how low the power/current rating on the motor was.

Thanks! I've learned my one new thing for the day.

I am unaware of any California plate after the 1920s that used white lettering. What year is that plate for?

There are a number of branding names or acronyms that I wonder about. How can some of these make it though any kind of approval process. All those trucks and SUVs that have the logo for Toyota Racing Development slapped on is one. It is just the initials and I can’t stop from trying to pronounce those three letters as a word. The first vowel that comes to mind that makes it into a word is a "U". Why would you want to proudly announce to the world that your vehicle is a piece of . . . If I were to get a vehicle with those decals on it I'd be out with a heat gun and a plastic scraper removing them the instant I got it home. Or maybe I just have a weird mind and nobody else sees it the way I do.

Unless they changed it when they went to an electrical sending unit, the temperature sensor location should be on the rear of the head on the driver side of the engine.

We inherited a Volvo with a 5 cylinder engine back in the late 1990s. Car was a tank, bad visibility to the rear corners, so ended up trading it for a car more to my wife’s liking. I don’t recall that the engine sound/vibration/whatever was noticeably different from engines with a different cylinder count of the same basic displacement and horsepower.

You might find it helps on cool damp winter mornings. When I lived in Sunnyvale, a bit milder climate than in the Central Valley, I found that if the ambient temperature was in the high 30s or low 40s and the humidity was up that there was some improvement in drivability when engine was cold. But it won't be a big difference and if you let the engine compartment warm up a little before driving it will be even less of a difference.

That is an odd engine number and I don't know what to make of it either. . .

I don't see a link in your post. Is it this one?

Nylon has a tendency to flow over time, I would be reluctant to use them on the kingpins on my car. Seems like the clearances and tolerances would go out of whack over time with nothing more than than just having the vehicle sitting parked. Maybe there is a new-fangled nylon that has different characteristics, but color me skeptical.

You might verify you have the correct bushing and U, there are variations on the size. Factory service manual should show the clearances and alignment you need. My manuals are for Plymouth for the 1930s and your 1940s Dodge truck are likely different than mine.

For the "silent U" style shackles, you place the "U" piece into its final position then screw the bushing onto the "U" and into the shackle or spring simultaneously.

I don't see a mechanical locking device. Not sure I'd want to be under something held up with only the hydraulics. . . But, assuming I am wrong and there is a mechanical lock, they sure do look like they'd be nice for garages like mine that have limited height so you can't use a big lift.