Similarity in gearboxes

There are some cars with similar engines and gearboxes, but I've noticed how little distinctiveness some Renault, Volkswagen, Audi, and Dodge models have regarding their engines and gearboxes from the front of the radiator. I'd like to know how to adapt the gearboxes and even engines between these four models, for example, from Dodge to Audi or vice versa, etc. Which one would look more original than the other?