Hi everyone, I'm new here. I recently aquired a '72 T-Bird with a 400/C6. 75,000 on the clock and unmolested. Main issue I have at the moment (that isn't cosmetic is the fuel gauge. Here's the story:

When I got the car, the gauge didn't work at all. Seller said it just "quit" the other day. No big deal I thought. Replace the voltage regulator. I'm no newb to classic cars or more specifically classic fords, so I tore into the dash, and took out the regulator. It didn't look bad, but I decided to rebuild it anyway using a 7805 5V transistor. Plugged it in and...nothing. Checked voltage. Dead on 5V.

Next pulled the sending unit. There's the issue! No float left! Replaced the float, cleaned the sender, cleaned plug and all ground points. Tested the sender with a multimeter on the bench. 86 ohms full, 20ish empty. Readings were on par with my ford service manuals. Hooked up to the car and even manually moving the arm, I can only get the gauge to read 3/4 at max travel.

Next I figured that maybe the gauge needed more than 5V to operate correctly, so I bought a NOS regulator off of ebay. Installed it, and now I have a functioning gauge again but....it reads consistently a quarter high. Meaning, 1/4 on the gauge really means I'm out of gas. Tried adjusting the new regulator by turning the adjustment screw (turned it at most a half turn each way)...no change.

Reinstalled my rebuilt regulator once more so that empty on the gauge will correlate to empty in the tank, made sure it was grounded properly, and still nothing. So as it stands now, my gauge reads empty fine, but when the tank is full to the point of spilling out of the car it reads only 3/4.

What should I check next? Been told I can adjust my gas gauge internally...should that be my next step? Or should I keep trying to adjust the NOS regulator I have?