I ran some gear ratio calculations for the 600 and 650 Watt motors using a 60 tooth axle sprocket and 16" wheels. A 60 tooth sprocket for #41 / #420 chain is the most common largest size sprocket available at go kart parts stores so that is the size that I ran calculations with. The top speed shown in the calculations is with the motor under load. The top speed will be a little higher when the motor is not under full load such as when on flat paved ground. The top speed will be controlled by the throttle at all times though so the wagon will go the exact speed that you want it to. Here are the gear ratio calculations:
For this size of battery pack a 36 Volt 4.5 Amp (or higher) battery charger is required for an overnight recharge. We sell 36 Volt battery chargers on this page: https://www.electricscooterparts.com/36vchargers.html
All of the parts can be purchased separately on our site, or we can make a kit out of the parts which is pre-wired with matching and labeled connectors.
Please let us know if you have any questions?