What track are you planning on racing this kart at?
Hardly anyone uses 5-lug rims on go karts, so finding the matching wheel mounting hubs will probably be difficult. You might consider building your own hubs/hub-adaptors, or using rims with a more conventional bolt pattern.
Even with a big 16hp engine, that 100mph gear ratio wont work. It'd be like a car trying to take off in 5th gear... Depending on your kart and riding conditions, gearing for between a 20 and 40mph top speed would probably be a more realistic goal with a 16hp engine governed to 3600rpm.
