If return lines aren't needed,then why did those"idiot factory engineers"design one for 78 & later trucks?You don't need a pressure reg-just make sure the return"orifice" is properly sized and is restriction free.
VR-i'm getting 3.5 to 4 with the above mentioned return line with w factory mechanical pump.
And yes,you can use either side for a feed.I have my FP guage in the un-used side.