The poly bushings are preferred by many, they rely on being lubricated, so in conjunction grease zerks need to be installed so they can be lubricated once a year. If not they will most certainly squeak.
The rubber bushings are offered by many of the traditional vendors, alternatively a guy on ebay 'Maseratisource' sells them. I picked up mine from him as did George Pence and we were both happy with the quality, price and service.
Maserati Source Bushings
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