In my case Holly makes it very easy, I didn't need a return line because they had a relief valve built into the pump. They make pump kits for Mustangs, Cameros and probably a few other cars. I'm also building a 1979 Ford F-250 4x4 w/ a 460 and will use the Holly system on that truck. I will have to run a return lie. Before I bought my 1st system I called Holly's tech section and spoke in length with them.
Go to www.holley.com ... They have several system on their website to look at. Download the PDF instruction and installation manual. This will tell you what all is involved in installing one of their systems. I have the MSD Atomic EFI and it is a great upgrade.. I would do the return system, it seems to make things less problematic.