Question about fuel gauge wiring.

Basic gauge readings


OEM sender
(gauge readings)
18 gallons = full to slightly over full.
13 1/2 gallons = 3/4 tank
9 gallons = 1/2 tank
4 1/2 gallons = 1/4 tank

after market sender
(gauge readings)
9 to 18 gallons = full
7 to 9 gallons = 1/2 tank
Empty to 7 gallons = empty