My existing Curtis system is 72 volt with 6 expensive batteries ( $2500.) with a small Amp Hour availability. 35-45 miles on a 6 hour charge is abysmal performance for a $20,000. factory built motor vehicle. My current estimate to revive this $500. truck is about $6000 in parts, that makes my decision for me and takes me to the Smart EV recycled option. No one has offered a generic upgrade solution, so the 9" motor mated to the 2 wheel drive Toyota designed transmission, batteries and 4 on 100 mm rear axle, will be out of the truck and on EBay by Sunday.
It looks like you are planning a complete powertrain replacement, including battery. That's a very different situation from just replacing the controller!
... they are readily available plus the drive motors have controllers mounted to the motor and gear reduction transmission, which gives me 4 wheel drive options. as I will have a spinning axle output facing forward.
If you don't use both outputs of the drive unit, you will need to lock the Smart or Tesla differential... or you'll just have the unused output spinning and the other one getting no torque. Zero EV offers a ready-made
spool to eliminate the differential, although only for the Tesla large drive unit.
Regardless of 2WD or 4WD, the gear reduction of the drive unit plus the gear reduction of a separate axle assembly will likely be excessive. Zero EV offers a
4.5:1 reduction gear set (again for the large drive unit only) to replace the stock 9.7:1 to address this; I doubt this is available for any other drive unit.
An alternative might be to place the drive unit in its normal orientation but at the rear axle, and build or adapt an independent suspension around it. This is a lot of work, but has been done. It would not provide 4WD, but would eliminate differential and gearing concerns, and would leave more space for battery packs.
Tesla and Smart traction motors are both "Gear reduced one speed, and simple to mount, as both have rubber mounting ears and both will give ample power to a 1500 lb. mini truck. for the upgrade to the Tesla, the infinite burnout capability would likely be worth the extra $1500.
Power, maximum speed, and torque are all limited by the battery, not just the drive unit... but yes, if you put in enough battery any production EV drive unit will be more than enough for a low-speed vehicle.
Any Tesla drive unit seems like an extremely heavy thing for the little Miles.