On the front axle of my '67 panel we installed 944NA disks and hubs by means of an adapterkit which I bought from Vdubcustoms.
Now for the back..you do not need to buy the expensive CE-hubs and drums. Find yourself (used) backplates, stub axles and drums off a late bay (that is, if you have a '68-70 bus with the 5x205-pattern). If you have a '71 or a '72, you do not need to buy any parts
Then install the parts as shown in the pics below (you should use late brake cylinders and brake linings as well, but you can leave the early handbrake cables in, they will fit on your new setup).
Here you see the early setup. Look closely and notice the (redrilled to a 5x130 PCD) hub, laying on the floor.
Here's why you need a
late bay stub axle (length). The axle of a late baywindow is a bit less wide than the early one.
Here the (late bay) backplate is installed, but you can re-use the early one. I bought new late ones 'cause I was not sure if the early bay parts would still be usable with late bay brake linings..which they were.
Final step is putting on the redrilled hub and drum and refit the axle nut.
Here is the final result; an early bay on 5,5x15 Porsche steel wheels.