From a recent experience one of the parts resellers AM has the Boss strut tower
braces listed as fitting the 05-09 Mustang GT's. Well, I tried this as the units looks great. The problem is that the width of the brace does stick a hood support at the hood scoop. Not by much, maybe a quarter of an inch. I noticed this by a slight rise in the back of the hood when shutting it.

For those considering installation of a brace this is a FYI.