I have to replace the stock fuel pump on my '68 (400), and I opted for an Edelbrock (part 1713). The stock has three lines, one fuel in, one fuel out, and then another fuel line going back to the tank, for which I assume is a vapor return line. ?

Can I just plug that line, because the Edelbrock fuel pump only has 1 in and 1 out. This fuel pump is for pontiac v8's.

I plugged the vapor return line on my Mr Gasket pump becuase i also didn't a vapor return line. Installed a return line is a good idea to cut down on vapor lock, which is why the factory did it.

just make sure the vapor line is plugged tight because I thought mine was until I filled my tank full and fuel began pouring out of the vapor line plug.... I put a bigger bolt in the hose to solve the problem.