Your bike is a Benelli Sport Special from around 1970. It seems pretty complete except for a metal strap that shoud run around the base of the tank and a few oher things. They were either 125 or 250cc. There was one for sale here in Australia on www.bikepoint.com.au I know the owner if you want a contact.
There is a tank and also a parts book for this bike on e-bay. I can get the numbers if you want. I'm glad Dobbinuk posted a photo as I was having trouble locating the one I mentioned. It is a good photo to work from.