I visited a junk yard this morning - 2 Eagles, no check valves. The first car is an SX-4 that just arrived this week but I think they stripped a lot out of it before it got there. I was looking and looking for the return line and could not find it. I finally looked at the emissions sticker and I got my answer. This car originally had a 4 cyl engine, therefore no return line and no check valve. It was interesting though because there seemed to be a lot more room between the engine and the firewall than in my car that originally came with the 6 cyl.
Second car is a 1980 wagon that has been there for a couple months. The fuel return line must have been replaced at sometime during the car's life, as there was no check valve. I'll keep hunting!