That looks fantastic Scott!
I'm sticking with the kit motor too.
If anyone needs one then they are really cheap
http://www.ebay.co.uk/itm/TAMIYA-NEW...item484faa583e
I'll be using the kit tyres until they wear out. After that I'll be using the cheapest rubber tyres I can find. Some cheap ansmann ones or something similar. I don't think tyres will matter a great deal running Tamiya silver cans.
Chris, about the diff screw, yep, you were right! I owe you a can of pop for that one.