That elbow line coming out of the sending unit is the fuel line to the fuel pump. Goes through the floor and joins a short flex line right under the floor. Then a hard line connects to the flex and goes to the fuel pump. Needs the flex connection to absorb the shakes, bumps and rattles from cab to frame. As had been said... it's a 54 tank but will work just fine in your 52.
The wire from your fuel gauge goes through the firewall, runs down by the master cylinder and up through the hole in the floor behind the seat and connects to the sending unit. Don't forget to ground the sending unit from one of the attaching screws to a good ground nearby.
