id do the 8.8 just for the sake of having a limited slip rear end, disk brakes, and a better gear ratio. From a performance aspect, it would be great.
Mileage isn't THAT big of an issue, since its fairly cheap to rebuild axles. My biggest concern would be the condition of the gearset inside the axle, so it would be a good idea to open it up and check how the gears are wearing. Look for shavings in the oil, examine the ends of the axle to see if the seals are weeping, etc.