**Brent beat me at responding first, hah**
You can plumb the return line, and main fuel line (just leaving an area for a pump if you are going with an external pump) and just wait till you have your set up to finish the "ends" of the line.
You'll need a fuel pump, pre filter, post filter (optional but recommended), a fuel regulator for the range of psi you will need. The system you go with will dictate what exact fuel pressure you will need, and the kind of injectors. But like several folks on here have mentioned, it will be in the range of 45psi +/- a few. You will also need to regulator to control the psi at the rails/injectors.
The way mine is set up, using the FAST EZ-EFI system goes like this: Tank, line, pre filter, Mallory pump, line, post filter, fuel rails (the TWM system has two rails so I have to put a Y before the rails to split the line in two), through the rails, regulator, return line back to the tank. Like I mentioned before, our regulator is set at 46 psi right now (what was set on the dyno) and I will try to get it closer to 45 as per FAST.
Hope this clears things up? Or did I confuse you more?
Arno