I had some issues getting the correct information from Lanner but he definitely confirmed its the earlier disc.
"Rear rotors are stock 83-85 944 NA, 289x20.4mm."
Hence why I've now bought these. I still have my original 986 disc. I've ordered new NA 944 rear disc and my the originals ones are here also. I expect Lanner has posted me my brackets now which will take up to 10 days to arrive. By then my car should have made its way back to me and I can confirm what I've got.
I've bought my disc from this place and they have all the information required regarding the disc.
http://www.mtecbrakes.com/brake-discs/porsche.html
proudbugowner is indeed correct about the Centerbores sizes being different for the 986 and 944.