Having a return line does a few things. First it keeps a supply of cool fuel in the carburetor. It all but eliminates hard starts due to vapor lock during warm months. It also takes a tremendous load off the fuel pump. The system is no longer a "dead head" system. It makes it MUCH easier for the pump to move the fuel. Not having a return line makes it more difficult for the pump to do it's job, because it always fights it's own pressure. Installing a fuel return line reduces that dramatically. Sure, you can run without one. Many cars did for decades. But ALL modern cars use them. It's NOT just a fuel injection thing. It makes the pump last longer, whether it's electric or mechanical and can approach the driveability of fuel injection if done correctly. I wouldn't build a fuel system without one. My rat truck will even have a fuel return.
One more thing.....and this is simply personal preference. IMHO, I think it's best to have the return come off as close to the carburetor as possible. In fact, when I do a hot street or race fuel system where I run a Holley, I run Dominator float bowls, because they are drilled and tapped on BOTH the passenger's AND driver's sides. This allows you to come off the driver's side with the return line, tee them together and run back to the tank. Stick a regulator in the return line close to the carburetor to act as the orifice. This regulates prressure even on the pump side of the carburetor, just as it's designed. I think that works superior because it allows fresh fuel to constantly flow ACROSS the fuel bowls constantly circulating. If you've ever torn down a Holley and seen the secondary side all varnished up, but the primary side beautiful, there's a reason for that. People don't use the secondary side as much, so fuel sits back there and goes all to hell. This is especially true with the ethanol puke we run now.
