Yes I did years ago. Factory Rear still in car.
I have spoken to two other A12 owners I know in the last few days and both have 11x3 rear.
One is a VERY low mileage car,
Other has been in family since new.

Also heard that they built the first run of A12's with 11x2.5 then later builds had the 11x3's.?

I found the drums and shoes I needed.

After looking online have found people with R/T's having 11x3 rears also.

I hope more owners chime in with what they have on their cars VS what we read they came with.