Aside from this kit, what else is needed to complete a set up? Very interested in this. Off road capability? Thanks

Our PRO2 Electric Skateboard Conversion Kit or our PRO3 Electric Skateboard Conversion Kit would be the best options if your looking for a full electric skateboard conversion kit minus a longboard deck.

As for Off Road Capability or All Terrain Wheels, we don't those wheels available at this time. However, we are working on offering 6" x 2" Pneumatic Tires in the near future 😀.

My motors have 10mm shaft. What is the centre hole on drive pully for the double motor 6374 mechanical kit as I couldn't see it in description?

Our motor pulleys are made out of steel. Drive wheel pulleys are made out of aluminum.
All of our motor pulleys have an 8mm bore. You can fit an 8mm motor shaft with a keyway (3mm x 3mm).