70s are going to add unsprung weight (not a bad thing) they can take up to 7.17 gears if you want them. Chances are good the front and rear will be 1.5" 35 spline. (rear might be 32 spline) If you forsee stepping up tire size and trail difficulty in the future, I'd say hang onto them.
If you sell, the rear would be priced well @ $150-$200.
For the front, it depends if it is open or closed knuckle. If closed knuckle, usually about $450 or so. They aren't a very sought after axle.
If open knuckle, I'd say $1100-1200 would be a decent price. Some might say it's high but there aren't many open knuckle 70s out there and if someone is looking specifically for that axle, they are willing to pay in that ballpark.
