I used the factory style hard line, Hemi sized 3/8 supply and bought a regular BB/SB 5/16 line for the return and ran them side by side. I flared the factory line with the GM push-on style o-ring fittings and bought the appropriate adapters. For example Russell Performance 644133. AG.
General rule of thumb is that the return line should be no less than the diameter of the feed line.
