The console pad in my '69 XR7 is also ribbed. They're very hard to find. BTW, CJ Pony Parts carries a wide variety of Mustang parts including interior parts. Many of the Mustang parts are identical to the Cougar parts and that holds true for the dash and console.
CJ has a console pad (PT# CONP), but I'm not sure if it's ribbed or not. It doesn't come with the hinge either.
Now that I am home I can check Mustangs Unlimited catalog. They show both styles available and only the flat one says it's a repro. Of course doesn't mean that the ribbed ones are originals. They are available in black only for $39.95 ribbed, $32.95 flat.