I have seen many builds where the lines are not covered with the gravel guard and to be honest I never thought about it.
Summit has them for $33.29 for 20ft.
http://www.summitracing.com/search?S...gravel%20guard
I will leave mine as they are, maybe in the future I will add the gravel guard if I see any small knicks on the line from driving (I hope I never will).