Our 71 did not have a return line and I never installed one. Also never went to an electric pump. Nowadays, I would, what with all I've learned about them. You should install some form of "rollover switch" or the like, to cut the fuel flow off in event of mishap.
An RV genset needs only a couple pounds pressure to run. I think the "3-5" or maybe it's "2-5" is good. For the road engine, the spec I've always heard is "5-7 PSI."
Our 360 starved sometimes. Say we wanted to get up to 60. We could accelerate hard in First and Second, reaching say 45. Then, in Third, it'd lay down on us. Reason was, the Load was still there and Acceleration was demanding fuel. Problem was, reduced RPM in Third didn't allow the mechanical pump enough strokes to provide it.
