If your using the Scavenger Hub drives you still need the center wheel hub from the 2.0 hub files for R2 to be drivable.
I have extracted those parts here if your doing an order to make it easier:
Process: Sheet Cutting
Material: Aluminum 5052-H32
Material Thickness: 0.125in

- Scavanger_Rev2_CenterDriveWheelOnly_0125.png (205.89 KiB) Viewed 35 times
Vex Robotics
2 qty 1.125" Bearing Pilot Plastic VersaHub (1/4" Wide, w/ Plate Sprocket Mount)
4 qty 4" Omni-Directional Wheel v2
4 qty 0.500" ID x 1.125" OD x 0.313" WD (Flanged Bearing) • $2.99 SKU#: 217-2731
(Updated guide on using the more easily available goBuild wheels is coming soon)
Home Depot
5 qty 3/8 in.
-16 x 4 in. Zinc Plated Hex Bolt
5 qty 3/8 in. nylon lock nuts
AluminumSpacer.com
4 qty Aluminum Spacer 1/2 OD x .382 ID x 3/4 Long
2 qty Aluminum Spacer 1/2 OD x .382 ID x 1-3/8 Long
2 qty Aluminum Spacer 1/2 OD x .382 ID x 1/8 Long
4 qty Aluminum Spacer 1/2 OD x .382 ID x 1-1/2 Long