Welcome to EBPF, Cbudden! Do you have the VIN perchance of the SHO you are looking at? You can get the window sticker here:
http://services.forddirect.fordvehicles.com/inventory/WindowSticker.pdf?vin=Probably looking at at least a spark plug change at the 42K mileage.
PTU fluid change should be on your short list as well, as dealerships typically don't service that (Ford says no need), though some may provide a BG-type service for it.
Check for cracked turbo piping (telltale signs might be dirt & sludge buildup on the exterior) and oil in the intake
Hose clamps are known to come loose
Knock sensor wiring should not be damaged, and should be taped well away from other surfaces (you can do this yourself later)
TSBs you can check for this MY:
http://www.ecoboostperformanceforum.com/index.php/topic,3836Otherwise, standard checks for any ride: fluids clear/filled/etc, drives well (no hesitation/stumbling), no leaks anywhere, etc.
Advise getting the Ford ESP warranty (cheap online) if you are keeping the SHO any length of time. To cover the electronics/climate control etc. if nothing else. Be aware that body panel coverage will be practically non-existent, so as curry said, check closely before you take delivery.
