This is what I used on my 2005 5.7

http://www.summitracing.com/parts/rnb-800-041?seid=srese1&gclid=CNWr5bnBrsgCFQ6saQodffELdg

that's 5/8

and yes, they were hard to locate for the application.

Tip, you can also use a small zip tie or tie-wrap. but for fuel, using the proper connector of the right material is best. To remove these, you simply push down on the top of it (the rounded part) and then pull back. this pushes the shoes down and out of their grooves