Can I ask what stroke do you need I to me and do you know the size of the main bearings. Check the conrods you've got are actually the right length you need and have the correct diameter little end bearing
There’s a guy who advertises on subitoIt and, I think, autoscout who seems to advertise a lot of used and remanufactured bits for classic and obscure Fiat (he even had a five speed box for and 850) and Autobianchi…if I can find the link I’ll post it