79-10 Mustang Yukon 7.5" 4.11 Rear End Gears at LRS - Same Day Shipping!
If I could make a suggestion, and that is to upgrade your rear axle to a 8.8". I'm pretty sure that an axle from an 2005+ will bolt right in. At least that's what I'm seeing. I don't know off the top of my head if anything was changed, e.g., gear ratio wise, that would make 05-09 rear end gears incompatible with 2010.
I would also check with Ford Racing for a FRPP or have you called American Muscle to check with any cross compatibility.
Also, I was doing some browsing and found FRPP gears, #M-4209-L410N. These were discountinued from Ford (I'm guessing this is when they handed over production to Motive performance). If gears from other years fit 2010 then I would try to find these since you can probably get a good deal on them.
BTW, one set of gears should be compatible for the last 2 or 3 decades, i.e., 8.8" gears will work from 1979 - 2010 (so says American Muscle), and 7.5" will work from 1979 - 2009.
But I'm really only good with 01-04 Mustangs and not as familiar with the S197 so I'm sure someone will chime in and correct any information I missed.