Big bolt pattern hubs.

You can just take your hubs to a machine shop and have them drill you to 4.5, same as your rear axle
I think the Scarebird install req'd drilling substitute rotors to a 4.0 pattern so that will be a redo also. I suspect a new pair of rotors would be req'd. How many different bolt patterns will fit in one rotor ?
Scarebird is a good option to get disc brakes where drum brakes were, but nothing more. Wheel options do not change. Might not be the best choice for everyone in the long run.