I have yet to see a "rear fill" rear frame mounted fuel tank that doesn't hang down like a ruptured duck. If ya think about it, the license plate is low, and if the filler neck is there the entire tank will need to hang below that point for it to fill correctly.

Here's an example:

http://i645.photobucket.com/albums/...20Truck%20Stuff/IMG_0912_zps13cee1d2.jpg

I installed a Chevy 49-52 passenger car tank in my '65 C10. It was one of the first things I did to my truck back in January of 2009:
http://i645.photobucket.com/albums/...Status%20Photos/GEDC1242_zpsba37b321.jpg

Here's the "How To" thread I created. It discussed where to get parts, etc.: http://talk.classicparts.com/showthread.php?p=88322#post88322/

More tank options here:
http://67-72chevytrucks.com/vboard/showthread.php?t=522264


In the Stovebolt Gallery ~~ "The Orange Crate" 1965 C10 SWB Step Side Build Thread

Inspired to be different. Different in a way of my own, not in a way that others strive.