fuel gauge not reading properly

[seinsmeld]

i have a 1983 stang with a 1993 interior. the fuel gauge used to read backwards [tank was full, gauge read empty, it wood move up 2 lines til it was emoty] installed a 93 tank with a 93 sending unit. it reads full when tank is half. 2ND ISSUE IS THE KEY, WHEN I TURN THE KEY IT SPARKS 1/2 TURN AND NOT FULL TURN. HAVE NEW KEY CYLINDER AND SWITCH.I ALSO REPLACED THE STEERING COLUMN.

PLEASE HELP

[Speedtospare]

- 79-86 Mustang Fuel Level Sending Unit Ohm Readings are approximately 73 ohms empty and approximately 10 ohms full.
- 1987-97 Mustang Fuel Level Sending Unit Ohm Readings are approximately 22 ohms empty and approximately 145 ohms full.

Does the car have the original unmodified fuel tank?

[seinsmeld]

Brand new tank from a 93 stang, new sending unit w float

[seinsmeld]

everything is new, i just took the tank down. everything works fine as long as the sending unit is not in the tank. once i lock everything together it reads empty. when the fuel sending unit and float r out of the tank it reads, when i put it in the tank it stops working. i dont know if its starting the car or bc its all together!!