An old tank does work well. I have made a few from 35mm film cases. The tranparent ones. Set it up just like your fuel can. Put a loop of fuel line on top. Just plug the brass that goes to the bottem of the catch can into the line from your muffler. When the catch can starts to fill up just reverse the pump until it sucks the fuel out. All i do is epoxy or JB weld two pieces of brass line through the lid of the film case. Make one go to the bottem and one just through the lid. Leave about 3/8" out the top. Put your 2" fuel line on each end and the catch can is done.

David