Gas tank will probably be off an early Monza
Rear fender will probably be a square style front fender from a later Monza Jr
Seat is an eBay special, along with the springs.
Headlight is unknown. Some Italian number probably used on various bikes of the era. One of the NOS parts Cosmo is selling on eBay.
Tail light is a Sparta copy.
Again, these photos are NOT of the correct parts. All in good time time...