fitting a larger engine to the corsa c shell is easy, mine took me around 24hrs all in and its the only one I know of that's on the road on the uk so no one was able to help with any part. all the mounts are oem, only parts that are not are the down pipe and L/H drive shaft but that's off the shelf from a corsa b 2L conversion.
fitting the z20let/h/r engine is as easy as a factory fit swap all parts and guides readily avalible.
do it right, do it once!!
over here all you need to do is to get a new mot, then change log book and retax unles you modify the chassis in any way then it gets harder to get mot.