Fuel level gauges

I don't know how you plan on doing yours, but I replaced the OE line with 3/8 nylon 12 EFI line for the feed and used the OE steel as a return.
Mine is carbed, but it sure was easy to deal with and didn't cost much to do.
As a side benefit when I got all done and tested fuel pump pressure I found that the OE steel line used as a return gave exactly the resistance to make the fuel pressure at the carb what it needed without having to put a regulator on it.