I don't think we can ever have too many Benelli race replicas, so good luck with your project, and I look forward to seeing pictures of the progress.
It looks like you will have to find some nice spoked wheels, perhaps with drum brakes too. I know that the exhaust pipes you are looking for are available for the 500 so hopefully you can get them for your 350. Try Selwyn. He should be able to advise you. His number is listed in the suppliers post at the top of this section of the forum.