Like you I am new with rebuilding my truck.

I have looked at several different tank installations and if you are a little mechanical it looks like a mid 80's suburban fuel tank will do the trick with some minor modifications.

Here is a pretty good how to: http://www.persh.org/Pickup/TankBelow.htm

good luck with the build.

http://s994.photobucket.com/albums/af62/ScottAz2/