[67RS/SSx2]

I think you can see the return line connection on my aux tank in the attached pic. I cannot imagine connecting a single return line to the main tank when multiple tanks exist. In my case if both tanks were full and I select the aux tank, the returning fuel would overflow the main tank and I would expect fume issues. Not to mention the aux tank would drain much faster if returning fuel was going to another tank.

I looked in the assembly manual. It does not show a fuel return system for the aux tank but it is only marked as 1971. Don't know if there would be any difference in a 1972 version. I also looked in my GM parts book but nothing difinitive there either.

Pbfut mentions the return line valve in post 12. Interesting...did some have return lines (and return line valves for aux tank) and some not? My truck has a 400 engine and was built in California. Wonder if any of that makes any difference?

Also attached a pic of the electric fuel switchover valve that was added to my truck. I do not have the original manual valve. You can see it switches the return line.

As usual I am all questions and no answers!