One thing to consider............. Your spool will likely weigh considerably less than a gear diff. This is rotating mass that directly affects the acceleration of your car.
Tamiya 417v7 Sedan, ___ Tamiya 417v7 USGT, ___ CEFEX EVO w/ 417 suspension VTA
Exotex TA06 Pro CS Drifting, ___ Tamiya 417v5 (sold)
AE SC10 4x4
AE SC10 AE B4.11