There was an overflow tank offered as an option in the parts catalog as early as the 40's. It's a metal tank that mounts on the firewall. Mounted one (repop) in the '48 2 ton.
http://s1276.photobucket.com/user/jsdesign2/media/20151230_210553_zps8zaatrdc.jpg.html
Just ignore the instructions to install it empty and empty it occasionally ????? just the reverse of what you want to do.