Supposed to be 125bhp

There is a little bit more to it than some people say on other forums. On top of what you said there is also the entire engine wiring loom, which also goes to the rear abs sensors. 1x engine mount needs swapping, fuel line connections are different and air filter box needs to be from the puma.
This doesn't apply to all conversions but I also needed to re use the puma exhaust manifold. This was because I used a late puma as a donor which had 2x lambda sensors and the older fiesta was only set up for 1x.

The drive shafts and gear box are the same yes, so are Interchangeable. But they have different ratios, because of this I chose to use the puma box and also because the puma donor had done 55k less miles than what my fiesta had done.