The Ducati Cucciolo (Puppy) engine design was offered to Ducati Elettronica at the end of WW2. They took on manufacture and development of the PULLrod 50cc 4 sroke, and had a success on their hands. It grew to 65 later and gained a 2 speed gearbox.
There were many thousands made, both by Ducati and their licencees.
Hi its a britax frame made for the 4 stroke 2 geared Ducati cucciolo engine the engine has external valve lifters they are hard to find these days its vintage is 1953 for frame and engine I intend to build it like a board racer with a fuel tank built from the head stock to seat tube .Looking for types of tank to make I do have a small cylinder type of tank that I might use.
You could talk to an exhaust pipe maker for 2 strokes and get a nice round section tank made. If you consider fibreglass, you'll need the correct resin; apart from that, it's just down to the hard work of making it and waiting for the stink of resin to leae your sinuses.