I have tried everything. I verified the sending unit is working properly by checking resistance in various positions. I confirmed electrical continuity from the sending unit to the instrument panel. I have a good ground on the sending unit. The flex circuit has good continuity along the traces. However, when I hook everything up as it is supposed to be, turn on the key and manipulate the float, the gauge does not move. I do not have a few of the engine sending units hooked up (water temp, oil pressure) because I recently switched to mechanical gauges but i dont see on the schematic how those should affect the gas gauge.

If you ground the sending unit terminal of the gas gauge directly, what does the gauge do? If you add a resistance between 0 and 90 ohms what does the gauge do? If nothing, check for power at the printed circuit trace. If power is good, then your gauge is not. The coil is visible from the back of the gauge, check for a burned appearance or a visibly broken coil wire.

what is the resistance supposed to be from the sender? I measured between 50 and I think 150 ohms

Joe, my '69 sender has 1.5 ohms at empty and 105 ohms at full.

90 ohms is the design spec, should be close to that to read with some degree of accuracy. 105 is reasonably close, but as the lower end is 1.5 on Lee's, maybe the meter wasn't zeroed?

I guess I'll check the resistance again. Do you suggest checking the resistance at the sending unit or the back of the gauge?

I had my sending unit (new sender from Classic) out on the bench when I checked it. Digital (Radio Shack I think) VOM. Looks to be reading properly. Needle does go past both full and empty a little.
I'd check it back at the tank. (Make sure both the sender and the gauge housing have a good ground.)

You need to test the sending unit alone, should range zero to 90 ohms with the meter zeroed. If you test through the gauge you'll come up with different numbers, but that will test gauge continuity as well.