closer to 200cc extra.. Your k50 gearbox will only fit a K engine as the bellhousing is cast onto the gearbox body.
T50s come with bolt-on bellhousings , type depending on what engine series they are to be used on and age. (K to T, T to T, A to T, Ag to T and so on)
Lots more info to be found in faq . Oh, and yes T50s are stronger than K50s and very different