635csi is a good car with definite appeal, racing heritage and modern performance. Every now and then one will pop up. Prices range from next to nothing for a complete dog too rediculous for a minter. Below a certain condition they are only good as donor cars. Currently the highest is an 85 for R130,000, and an 82 for R125,000 and average is around 70,000 for a decent condition one. Personally i think sellers are overestimating the market for these cars and this is backed up by the fact that most have been on the market in excess of 6 months. Beautiful cars... but you need to sell to an enthuesiast and for R70,000 you might be better off with something else.
Trim levels vary and the pre 82 models are a completely different car to the post 82 models. Outwardly the only difference is the rear bumper, foglights and antennae position. Beware that some cars are second hand imports so while it is registered and listed as an 84 it may be a pre-82 car.
They are hellishly expensive to restore. And there are not many is scrap yards.