A member named 2phast is exceptionally knowledgable on the subject. Check out his website -- he covers the upgrade in great detail:
www.2phast.com
His site covers the upgrade on a 201, but it's my understanding that the brakes are interchangable between 201 and 124 models.
Again, check out the web site. I'm merely a casual enthusiast. 2phast is clearly an expert on the topic.
Jeff Pierce