Some people do while others don't want to cut up their cars to install a gas tank that hangs down too low and looks out of place. The best bet would be to try and use a fuel pump module in a older tank. That would require installing a sump or something similar.
__________________ 2003 Silverado SS LQ9
1970 SS396 Elcamino
1970 SS454 Chevelle soon to be LS2/M12
that is an option but sometimes there are fitment issues that come with the newer tank. in my case my chevy '87 c-10 came with throttle body setup. its was easier to switch to a higher psi fuel pump which cost me $130.00. no measuring, cutting, or welding. cant get any cheaper /easier than that.
i have a 1980 Trans Am. with a 21 gallon tank. I figure anything smaller should fit. so maybe im just thinking too car specific.
But I figured if i took a tank from, say, a fuel injected firebird, it should fit? Is there anything special about the gas neck? can i just cut a hole and make a new one? (fills up in the rear)
Late model tanks tend to be thicker in the middle. If you are lucky enough to have a car in which they offered a fuel injection setup in later model years then you are set. In my case with the Chevelle I either have to cut a big hole in the trunk for the tank to stick up or use a fuel sump in the bottom. I bought a stock appearing spectra fuel injection tank with electric fuel pump for my chevelle with discount for $425 shipped to the house. Have yet to use it.
__________________ 2003 Silverado SS LQ9
1970 SS396 Elcamino
1970 SS454 Chevelle soon to be LS2/M12
Check out the gas tank for a 89-96 Caprice/Impalla. They have the fuel pump in the tank, fit between the leaf springs on a 1st gen F-body and the filler neck is at the rear. You'll have to cut you're trunk pan to make it fit. Or just get the trunk pan and tank as one piece from the junk yard. Worked for me on my 68 camaro project.
why do people buy gas tanks period? I 've been running a stock tank with stock pickup and an external pump for 2 years now
Depends on how you plan to use your car. For a frequent driver the external pumps are a lot noisier. Plus the internal pumps are cooled by being submersed in the fuel in the tank. With my internal pump, I don't even hear it when the car is running. For a race application, or if you don't mind the noise, the external pump seem to work fine. Especially for a drag car where the pump does not run for extended periods and have a chance to get hot.
Those are my thoughts
Pat
__________________ 1953 Studebaker Starlight Coupe Custom, 2000 LS1, LS6 manifold, valve springs & PCV, ETC, Sanderson Headers, 4L60E, Yank Stealth 2800. 68 Nova Subframe, Ford 8 inch, 3.80 posi. 13.68 @ 102, I need traction!
Swap Journal: http://www.hotrodders.com/forum/jour...ge=1&reverse=0
"Its gotta be bitchin', its gotta be low, and its gotta be drivable." - Fat Jack
Carb to EFI gas tanks 
1953 Studebaker Starlight Coupe Custom, 2000 LS1, LS6 manifold, valve springs & PCV, ETC, Sanderson Headers, 4L60E, Yank Stealth 2800. 68 Nova Subframe, Ford 8 inch, 3.80 posi. 13.68 @ 102, I need traction!
