Here's an idea that was posted not long ago.
http://www.67-72chevytrucks.com/vboa...d.php?t=456869
I don't know if I would use that tank. I would suggest doing some research to see if you could install a GM sending unit in that tank so that your GM gauge will work.
Depending on what your budget is, there are 2 board vendors that build very nice aluminum fuel tanks. Check them out over in the Vendor Marketplace.