They are 5x8. The depth is only an inch and a half I think. You can use the car outfiter at crutchfield.com to make sure your chosen componet set will work.
ive got an escape and just got 6.5 components i think it was 6x8 stock or somthin. we had to cut like 1/8" or so to fit the 6.5 in and just use like 1/4" mdf to make an adapter
I've used 6.5s in all my Fords since 1996 and didn't need to cut to squeeze them in there. I owned a 1996 Thunderbird, a 2000 F150, and currently own a 2006 Mustang GT, although my mustang no longer has 6.5s in the 6x8 location.