Yes a carb engine should have a fuel return, but many have since webbers bodged on at some point and had the return plugged up.
You'll need to remove both fuel lines and replace with mk2 gti lines, and fit the main pump & lift pump from one while you're there.
I'd recommend you fit a complete MK2 gti digifant system, and put a MK2 pb head on the 2e block, it flows better and you'll can just get a digi loom & plug it straight in

Edit: thinking about it, if you're using the MK3 pump you may be fine with what you've got! I think the only difference between mk2 carb & digi lines is the length & shape. Looking at ETKA, both digi & carb use the same flexi fuel hose
