would like to know what to get a gas tank from for my 72 c10 i have one from a chevy van but its a little too big .  

Where are you mounting it? If you want to mount it where the spare is I have used Blazer tanks.  

www.quantaproducts.com. over 500 tanks to chouse from.
I am useing a Jeep Scrambler 78-86 15 gal. in my 63. I am going to run the filler through the frame. Goung to weld in a larger tub with box plate. There is no real stranght conserns after the rear end other then hold the bumper.  

i appreciate all the info i can get ,i have built a few of these trucks but have never re-located any of the gas tanks.  

I am going to use my origanal sending unit.I plan on recuting and shorting the float to work in the new tank even if I have to cut the mount out and weld of swet solder it to the new tank.