I'm currently running a AOD with a 3.80 ratio posi (8' rear) in My 64 Sprint. The rear wines starting at aprox. 60 MPH. - It's, new, Motive gears, and I've had the set-up changed 2 times by reputable builders, and same result. -- This is, strictly, a street car, and I'm considering switching to a 3.0, ratio, open rear. My tires are about 26" tall. -- Performance is not a big issue, it's just a cruiser. -- Will this (3.0 ) work OK ? -- The other option, is to try a 3.80 ratio US Gear set-up, and keep the posi. -- Everyone will likely say stay with the 3.80 ratio, but, again, will the 3.0 set-up work OK ?