From the video footage I have seen, the Schnitzer cars at the NM500 were Group A from 1987-1989, and then from 1990-1992 they were DTM spec. cars. A friend of mine has the 1990 NM500 winning car (in NZ) and it is definitely DTM spec. I have recently organised the purchase for another friend of the 1992 Schnitzer car, it is in NZ now and also full DTM spec. Not sure how many people realise there was a difference between Gp.A and DTM, (and quite big differences too!)
Conrad