I decided to at least see if it’s possible before considering a chinese board. So, I have this Sector9 board:
It looks like it has 8" gullwing sidewinders I have a motormount you can 3d print and epoxy to the truck. But its for 10" trucks. You’ll need flywheels http://m.ebay.com/itm/281661805302. Pulleys can be 3d printed. Turningy sk3 6354 motors. Dual vescs. 500$ is not enough though. But a chinese longboard wont satisfy you at all …
you can get those specs with a single drive. but only just. another 300 at least for a dual drive.
Are there 500W hub motors available for DIY? I would assume they would cost less than the equivalent belt driven motors because of the extra parts involved.