Fiat gearbox on to Steyr Puch 650 engine

[Big Al]

I am looking at the Autobianchi. Its a nice car but after the failure of a half shaft it going to have to come apart. I have the makings of a Steyr Puch 650T engine. It is significantly more powerful than the 126 mildly tuned engine that currently sits in the Bianchina - the original special 500cc engine is long gone. The Puch is most definitely the better design for revs and smoothness as its balanced so much better. It also uses superior materials.

However the Steyr Puch gearbox does not fit into the Fiat Fiat 500 engine bay. You need to change the gearbox. I have seen  films and pictures of this, write ups claim a much better car to drive. But nowhere can I find the details of what you need to do to effect the change in gearboxes. I know it does not just bolt on. Anyone ?

To those drawing in breath. Is a Bianchina so much more wrong with a 125 engine, then the Austrian 500 clone versions engine? With that extra power the little cabrio becomes a marvellous second car for sunny days, and will happily keep up with traffic. Great also for doing foreign events where no convoy is available, or a cheap timed ferry ticket is used. Be great to nip over and do the Belgium Rally for instance.