The fuel sending unit on my 41 grounds on the outer sending unit flange to the frame near the tank. The gauge needs to be hooked up correctly or you will cook it...the E side to power, and F side to fuel sending unit.

Your speedometer screeching issue may be a dry bushing. Check out the tech line for the location of the felt wick. You have to remove a very delicate brass soft plug to gain access to the felt wick to add oil. Be careful as it is easy to break.

http://www.stovebolt.com/techtips/gauges/speedometer/index.html

Ammeter gauge sounds like it is good but you have charging issues. I am currently (pun intended) chasing gen/vr issues myself so I am not in a position to offer advice.

Oil pressure...is something stripped or cracked? If a 40 is the same as a 41, I may have a good used one you could have.

Temp gauge...one out of five...at least 20% are okay.

Paul


1941 Chevy 1 1/2-ton WW2 4x4 dump truck
In the Stovebolt Gallery
Lots more pictures