The normal Fiesta RS Turbo wheels are 14 inch 6j most of the 15" I looked at were 6.5j. at the time only the team dynamics pro race type wheels were 7j. I wanted to be able to fit bigger disks and calipers under my wheels but not stray too far from the geometry ford had in mind!
I use modified sierra 4x4 setup - I had some new pistons machined out of stainless steel so they will never rust and seize!
I really wanted to get the bleed valves done the same or in titanium for the same reasons but haven't been able to yet!