need help with temp guage

[Rescue 1]

Okay I need help figuring out a problem with the temerature guage on a 1972 Chevy 3/4 ton. The truck has a guage package and it appears all the other guages are working okay. The problem is the temperature guage goes clear to the right, indicating a hot condition. The engine is not hot, it will go over there with just the key turned on.

I assumed it was a grounded wire, nope. I checked wire with ohm meter with no shorts indicated. So I assumed the sending unit was bad, nope, changed with new one, no difference. So I went after the guage itself, changed it, no difference. Go figure all the major players changed and no difference.

I have had it all apart several times. I have checked the sending unit resistance, it has less resistance as the engine warms up. I don't know how many ohms it is supposed to have cold or hot, any help on numbers?

I took the dash apart again today and checked the printed circuit, nothing unusual. (no burns, breaks, etc.) I started probing the guages themselves, here are the results.

Temperature guage four posts: all four have continuity on new guage, only three on old one, none to case itself.

Fuel guage three posts: all three have continuity, only lower post has continuity with outside case, does this indicate a shorted guage? When hooked up normal all three have ground to cluster, when hooked up so case doesn't touch cluster, fuel guage doesn't work. Temp guage still goes over.

When fuel guage is hooked up the temp and fuel guages have grounds through the cluster, is this correct? If fuel guage is unhooked temperature guage does not ground with cluster. When I say cluster I mean the metal part of the guage/dash assembly.

Could it be the fuel guage is shorted and the temp guage is showing it by grounding through the sending unit? I have checked the grounds on both the dash and the engine, they appear to be okay.

Okay electrical wizards give me your best advise. I have been told by many apeople just to change it to a mechanical guage, but I don't think it would look right. After all it is a 1972 3/4 ton 4X4 that has only 16,000 original miles...