I just finished doing that job, literally about 10 minutes ago, on my 1985 300D. I tried to get the driver's side bushing on without removing the master cylinder, but I couldn't make it happen. There is a post somewhere on this forum where the guy did it with the master cylinder in place, but I don't see how he did it. Maybe if you had two people - one pushing on the bracket and one threading the nut - you could do it. In the end, it's probably easier to just take out the master cylinder.