[Dusten]

The fuel rails won't fit. A 5.4 is wider. The 4.6 rails are too narrow.

Stock lightning rails are pretty easy to come by.

 

[Dusten]

I have a set of stock lightning fuel rails but they’re return style and the mustangs stock fuel system is returnless. If I can figure out a way to make it work without having to redo the whole fuel system that would be ideal.

You can't. You can either run aftermarket rails or go return style.

 

[Dusten]

I’m potentially interested. Are they returnless?

No. The 5.4 had a return style system.