I was going to go shopping fuel line hosing today when I noticed that I was probably in trouble...

I swapped out my 260z fuel tank for a fuel tank from a 240z (was that bad?). The first thing I noticed today was that the 260z has two equal sized fuel lines running from the front of the tank towards the engine. The 240z seems to have two different sized fuel lines running (as far as I can tell from the 240z's gas tank). I checked whatever reference manuals I had but they all located the fuel lines on a different place on the gas tank, lower and more center, and they seemed to show that they were of equal size. Should I just use an adapter to connect the smaller fuel line to my 260z's fuel system (since the 260z gas tank had two equal size, one of the 240z gas tank has a smaller line running out of it) or do I have to look for another gas tank? Sorry if this is unclear.

Using the old gas tank unfotunetly isn't an option

If your car is carburated, there should not be a problem. One fitting is for the return line for fuel not pumped into the carburetors. (probably the smaller fitting). Try to look into the tank from the filler connection and see if you can tell which fitting has a pipe that is plumbed to the bottom of the tank. That one should be the "outlet of the tank" that supplies fuel TO the carbs. the other one is the return line carrying excess fuel back FROM the front of the car back to the tank.

Another way to tell which line is the return line with it out or in the car is to have about 3 - 4 gals of gas in it. Use an air nozzel from an aircompressor and blow gently in the holes - one will 'make bubbles' ( the pick-up tube ) one will not ( return tube ).

- Jeff

Thanks for the feedback guys, I'm glad I won't have to go looking for a new tank. I didn't get a chance to put your advice into practice today but I'll check on it and see what I can come up with.