Yeah, odd to start with a Group 4 body kit for no technical reasoning THEN add parts to make it look right without considering the technical impact on driving.This OP is just all over the place. Random facts and desires with no basis in the reality of improving an E9. I can't even imagine steering a car on the street with those huge front tires. This is an example of someone who needs to actually use and enjoy his car before making changes. A faux racer for the street threatens to be a worse car than one modified so much. Not sure this will end well.
I lowered my 635, and added very hefty sway bars and Bilstein sport shocks ab out 15 years back The car handles OK, but it rides like a truck. Nearly zero body roll, but super harsh ride. I may dial it back after I finish my Coupe project.