Sean Hyland Motorsport went out of Business a few years ago so they no longer exist as a company so i am sure it would be fine but not needed as honestly having looked extensivly into mapping of the SV and other Mustang deriviatives there are plenty of places you can get it sorted in the UK or the US
I am sure Chris can do it at Retro for the 260 but you could also speak to a US tuner VMP, Lund, Steve Shrader etc who have tuned many Mustangs and swap vehicles.