I made my own return fitting by using some brass fittings and a carb jet. I was told to locate the return fitting as high up on the fuel line as possible, then route back to the tank. I had these pieces laying around so once I was done, I started out testing with a couple of jet sizes and I ended up with a .052 jet as the oriface size for the return.
I took the brass barb fitting and tapped the inside for a 1/8npt thread. Then I took a 1/8npt plug and drilled/tapped it for a Holley style fuel jet. I started with a #60 and the idle psi was around 6.5psi. Then I swapped in a #52 jet and the idle psi went up to about 6-3/4psi or so. My electric fuel pump is rated at 7psi and I do not have a return regulator. (If I remmber correctly, the QF carbs are rated at 7-7.5psi at idle).