The hubs are yes.
And the cush drives will interchange also, but the spacing is different for the sprocket mount on the cush drives on the later models...so in other words a 78 cush drive and a 72 motor, no...your drive chain alignment will be off. 
However you can use an front offset sprocket on the motor if this becomes an issue.

So'full Garage

"Time is a Devil in great disguise"
- Leon Bryan Pretorius