The return line is worth the effort. In my experience, the cars without them tend to build up pressure in the fuel system when you shut it down hot, force fuel by the needle/seats and cause the carb to flood some extra fuel over into the intake, then they are hard to start if you try to start them back up in 10 or 15 min. after you shut it down. I added a return line to a '65 that didn't have it and it cured that problem.
So in my opinion, the return line is definitely worth the trouble.