So I installed a float style sending unit on my new EFI tank from TanksInc.
I have all the wires soldered and hear sink, I bench tested it everything works even now with a voltmeter I can put it on the post from the sending unit and I can see that I have 43 ohms. It's a factory ohm with 73-10 ohms. When I filled her up with fuel the most she showed on the gauge in the cluster was 3/4 full. For reference this gauge cluster has been in the car for about 10 years but I never connected the fuel gauge because the Chinese sending unit in the factory tank was always reading zero. I had installed an auto meter fuel gauge in my glove box with the appropriate ohms reed style in the tank. Don't get confused by all that all I'm trying to say is the fuel gauge in my cluster that's been professionally rebuilt has only been in use for 1 month as I had disconnected the blue wire going to it.

I disconnected the terminal connection in my trunk to the new fuel float. I connected a jumper wire from the cable that goes to the fuel gauge and the other end of it going to a verified ground and my fuel gauge goes to full instantly. When connecting back to the fuel float I don't get a reading.

Where is my culprit?

Could the blue wire going from the fuel gauge in the cluster to my trunk be broken somewhere in the loop? When I drove her from a car show a few weeks ago I saw that the needle on my fuel gauge was going up and down even though I was at a stoplight, as if it was pulsing. When I passed the new wiring I ran another blue wire along the length of the car along the loom on the driver's side as a precautionary measure in case I have to replace it.

When the tank is full, what ohm reading does the sending unit have?

What does the gauge show with the sender at it's current 43 ohms?

Is the sender grounded?

I put an OHM meter at The wire coming from the reed sending unit and I had begun with 5 gallons and I saw that it was still hanging around 70 ohms. I put another five gallons in there and I saw that it went to 58 ohms. I went and picked up some more fuel put it in there slowly I put another 5 gallons in there it showed me 25 ohms and then I put the final five gallons and it shows me 10.8 ohms.

The ground of the sending unit is on the same screw as the ground for the fuel pump. The fuel pump is working. It's a clean contact bare metal. I attached it to the spare tire mount in the trunk so it's grounded through the chassis 100%
The gauge on the cluster barely moves right now when it's connected to the Reed sending unit. When I first filled her up the best I could get was 3/4 of a tank

confused.
you put in a new sending unit.
it read 3/4 and now it doesn't read anything?

but it bench tested fine and showed full at the top?

could be the float needs adjusting to hit the top, if it still sends. you just need to bend the arm to make it hit the top when floating.
if you are getting power back to it, from the wire to the sending unit then you have connection.
if you have the original VR in the dash, it should blink with a test light.

There's nothing to adjust on the float level. It's this style

so how tight is it on the arm?
does it go in at an angle?
I recall some of those had issues where it binds up floating at a bit of an angle and won't continue to rise.
so it does still send, just not good enough to show full?

Goes straight down from the top

so the only things left to check is
is the vr voltage correct
does the float in fact reach the top when the tank is full.
like could there be an air bubble there.
is the gauge actually correct for that resistence.- I would try the 2 AA batteries in series to see if it reads half way for 3 volts instead of just grounding out the sending unit wire.

Agree, sounds like the sender is doing what it should. I'd try getting some ohm readings between the connector in the left kick panel and then ground. It should match the sender readings.

Even better if you can access the back of the cluster.

The gauge in the cluster should theoretically be brand new. I had the cluster restored by Gentry yet Auto instruments many moons ago. It was the only gauge not connected in the cluster because the Chinese sending unit couldn't talk to it. My next step is the voltage regulator. And they aren't cheap. Cheapest one I found is like 35 bucks. Beyond running a new cable to the fuel float all the way to the gauge and replacing the voltage regulator on the cluster I think I'm going to be at a loss. It has to be one of those two things because I've bench tested the float by tilting the fuel tank when I had it out and it was reading correctly the entire way. It's only when I connected it to the vehicle circuitry that I couldn't get the same readings. There has to be a break in the circuit somewhere

That's what I'm getting at, excess resistance in the wiring.

If the other gauges work correctly, it's unlikely the regulator is at fault.