Why do all you people want to change to mustang bridges? I have a 62 and a 63 jazzmaster. The 63 came with a mustang bridge and sounded dead compared to the 62. After talking to a few baffled guitar techs about it, who said it must be the pick ups i found one guy who found the problem straight away. He losened the strings, put an original bridge in, tuned it up and brought the guitar back to life. Its got something to do with diecast compared to steel. Musting saddles are diecast which evidently kill the tone and this is why my guitar sounded dead compared to my other one.
With both of these guitars i had all the bridge problems pepole talk about but with a high quality set up none of them are an issue.
Don't replace the bridge just pay an expert to set the guitar up right. Its worth the extra money for a quality set up.