I definitely wouldn't say the MIP axles are overkill. You'd be surprised how much torque can be put on the driveshafts when using low gearing and a lathe motor. I grenaded the stock shafts on the second or third pack. I haven't had any problems with the axles though. If anything the weak point there is the aluminum locker.

The Stampede shafts are a direct swap. You can use Stampede ends or the stock Axial steel ends. I've been running Stampede shafts in my Axial with the Axial shaft ends and yokes for about six months without any breakages. Had MIP sold those driveshafts when I bought my AX10 I would have definitely gotten them.