Need help with early SWB rear brake upgrade

[dsfnctn]

I am installing all of the parts that I can fit off of a wrecked 82 SC into my 66 912/911. Well I got the front suspension, in but I am having problems with the rear brakes. Has any body had any luck with a conversion to vented rear brakes on the short wheel base cars. I have heard the stock "S" rotors and calipers are hard to find. Before I go and chop and channel the rear bannana arm to make clearance for the rotors and smaller brake shoes and different spacing for the caliper I was wondering if anyone knows of a set up off of another kind of german car that is closser to fitting the SWB dementions.
Thanks