I have chased an annoying clunk in the front end of my 505 and even had the towers and shocks replace to no avail. [so much for the experts] UNTIL; I found that the bushes on the front radius arm cannot be tightened up beyond a certain point. You can buy several large washers (I used the centres out of a small angle grinding disc, a bit rough I know) and pack them in behind the large dish washer - you'll need to Jimmy the radius arm back a bit - but it will be like driving a new car when done. Fixed my wifes 504 as well, beudy.
Regards Felix