The Stock 75 bumpers are simply hideous. Luckily it is fairly easy to swap them out for the older style. This month I swapped the rear bumper with one from a 70-73. A very good explanation of the procedure can be found at BMW 2002 FAQ.
Basically you remove the old bumper…
Clean everything. Remove the caps protecting the old school bumper mount locations. Drill 1 inch access holes inside the trunk to install the bolts.
Install four bolts to hold the bracket and one on each side with a spacer to hold the ends to the quarter panels.
After I learn how to weld I will go back and fill the holes left behind.