Merle Coggins

While you’re back there, check the resistance of the sender wire to chassis ground. You should get somewhere between 10 and 90 ohms, depending on the level of the tank. If that’s an open circuit that would account for your “E” reading and you’ll have to diagnose the sender or the wire going to it. Temporarily ground out the sender terminal at the back of the gauge wit the key on. The needle should go to “F” quickly. If it doesn’t you have a faulty gauge. 

There are no bushings in the throttle linkage. It was just considered a maintenance item to add a couple drops of oil to the joints periodically. However, if you have lateral movement of the throttle pedal you probably have an issue with the 2 ball studs that mount the heal of the pedal. These should keep your pedal from moving sideways.

Yes, that's likely the casting date of the case. I've never seen a model ID listed for these transmissions. They're just New Process 4 speeds. I believe the later version is refered to as the NP420. Non-synchro vs. synchronized transmissions refers to how the sliding gears function. In the early spur gear, non-synchronized transmissions the gears have straight cut teeth and there are no synchronizers to aid in shifting. With these transmissions you need to learn the art of double clutching your shifts. The later, synchronized, version was introduced into the Dodge trucks in '51. This transmission has helical cut gear teeth for quieter operation and syncronizers on 3rd and 4th gears for easier shifting. Pretty much all modern transmissions are of this synchronized type now. 
 
Another way to know the difference, and how I identified this one, is that on the earlier spur gear units the PTO drive was ahead of the fill/level plug whereas the later, synchronized, units have the PTO moved rearward with the fill/level plug towards the front. 

Your B3C and B4C should have the same size bed, but the bed board layout in the B4 will be a bit different. More boards, and narrower each. The B3B would have the narrower, and shorter, bed than the 3/4 ton versions. 

You need the proper drum/hub puller to get the drums off. They are on a tapered shaft and will be tight. 

If you don't run the nut on tight they should come back off without an issue. Just set them onto the axles and measure. Shouldn't be off my more than a 1/4" or so.

That is NOT normal. A fully charged 6 volt battery should have 6.3 volts and you should never see the voltage drop to 3.8 when trying to crank. Either the battery has no capacity or only has a good surface charge. Another possibility is that the engine can't rotate and the starter is stalling out causing a high current draw, which will pull down the voltage, but not that badly.
 
Have your battery load tested and check that the engine can be rotated by hand. Either by putting a wrench on the crank pulley and cranking it over, or by turning the fan blade with the belt tight. You could also get under the car, drop the clutch inspection cover and try prying the against the ring gear with a large screwdriver/pry bar.
 
Merle

It looks to me that your "used" clutch disc doesn't have an even friction surface and is causing the chatter as it engages. Basically it grips and slips until it is fully clamped down by the clutch.
 
Merle

Is the groove you reference in the seal area or in the bearing area? If it's on the seal surface you can use a Speedi-sleeve to make a smooth surface for the seal. They are sold by size, so you'll have to measure the diameter with a good caliper or micrometer.
 
If they are in the bearing area you should be able to polish it smooth and go with it, as long as the bearings still fit well on the spindles.
 
Merle