Masters Productions from France makes a resin banjo drivetrain conversion set for the Tamiya 2 1/2 ton truck.It is the only one I have ever seen.With a little work I am sure you could make it work with the italeri.To order you have to go to the Blast Models web site from Europe.They carry Masters Productions products.I just checked and they show it availiable for $19.79 US,but remember the shipping coming from Europe.You could try R+J Enterprises at
http://www.rjproducts.com in the US,they advertise that they can get Masters Productions products.Hope this helps.