You can use, of course, one of the four ECS fuel tank vapor line for your return. I'm not sure its designed for pressurized liquid fuel return, but it will probably work. You can road test the concept using 30 feet of rubber tubing, to connect the fuel pump to the tank and give it a try without a big investment of time.
The factory returns fuel using a different line.
I believe the correct fuel sending unit for 440 and 426 cars with the vapor return line from the engine, have a second nipple fitting on the sending unit. The second fitting is used for fuel return. The unit may also come with 3/8 fuel line instead of the 5/16 found on most other engine models.
There is a also factory hard line, found only on the 440/426 cars with the engine fuel separator. They make this line aftermarket, if you want to install and use that for fuel return, it may look darn good and original.
The presence or absence of this fuel vapor separator return line, has helped me many times, over the years, in confirming and validating claims about 440 and Hemi cars. Without a VIN to confirm, we can drop to our knees, and look under the car for the K-frame skid plate and vapor separator return line. When present on a 'Cuda, they indicate an original 440 or Hemi car.