These older BMWs are becoming so rare future generations will not be seeing these "real"cars on the road, Hell I havnt seen one like this on our SA roads , I don't understand the point of Modifying them to give them more power, why not appreciate them for what they are , and have a unique piece of motoring history with good stock performance and a unique driving experience with you while your at it.
If you want a more powerful car , and your going to spend so much on power , why not just buy a new more powerful car .
This is just my opinion.