I have a 70 Dart with the slant six. The gas gauge never reads above 1/4 tank. Do I need to drain the tank to change it? Also, I see that part suppliers list a 3/8 or 5/16 inlet. Is there a way to tell before I take it out? Thanks!

Just measure the diameter of tubing protruding from tank before rubber union to fuel line, and or fuel line. Unless monkeyed with slant six uses 5/16" line and sending unit all the way to carburetor.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Does the fuel gauge actually move some as the fuel level varies?

If you have a volt/ohm meter, you can check the sender in or out of the tank. Measure the resistance (ohms) of the sender element to the ground ring of the sender with the float held to the full and empty positions. It ought to read in the low 70 ohm range when empty, around 10 ohms when full, and mid 20's ohm range at half full.

Not necessary to drain the tank but it sure makes it easier to remove and install! Siphon out what you can and then drain the rest out when you get the tank out. When you drain out the last dregs of gas, look closely for rust particles.

The gauge does mve some. By what you sre saying, is this an operation that involve pulling the tank out of the car? Thanks!

No, you don't have to drop the tank. Yes, you should drain the tank as much you can. You can get away with leaving maybe 1-2-3 gallons in it but the rest will come flooding out depending on the angle you have the car at when it's on jack stands.

But I would encourage you to drop the tank anyway to check for rust/crud in the tank....pretty common on anything this old.