So look this can be easy or hard. There has been discussion about fuel lines over the years, one recently going through a lot of material spec data on the application. Might be worth a look. To get you up and going TOMORROW you can remove all the rubber lines in the set in one fell swoop if you want, or just the leaking return line. From your photos, it does not appear to be the return line thats leaking, but one of the primary feeder lines to the individual metering pumps.
Regardless of which... you can simply hit your local O Reilly Auto and buy some Gates Safety Stripe line. 1/8" for the return line (starts at the end of that metal line, goes up and over the engine, then down along the skid back to the fuel tank) or 1/4" for those primary lines that go to the metering pumps.
On the return line, there are also 1/8" plastic vacuum tees. They might be reusable, they might not be. Buy some if they have them as backups. The line is a push fit on them and on the barbs off the fuel injectors.
On the primary lines, you will need to
carefully cut that metal band and remove the compression fitting off the pump side. You can replace it with the 1/4" Gates line, and some hose clamps. If the compression fittings are still strong on the pump side, you can use those... as they cause less interference issue. You might need to loosen the cast iron hold downs as you go on each cylinder, to install the hose and clamp and make sure the barbs are all rotated as far open (towards the push rod tubes) as each one can be... while being uniform position over all cylinders.
