the book shows the fuel lines going into the tank side by side. but my 2/78 280z has them stacked. which one was the feed and which is the return?

Top is feed, bottom is return.

when both are disconnected the return leaks fuel and the feed does not. is that right? i can suck it out but it doesnt leak on its own.

I've never tried that but I know that the upper hose is the one that connects to the fuel pump inlet and the lower one ultimately connects to the pressure regulator after passing through the lines that lead it there.