What is required to modify a 990 to 990S

[JacoM]

Let's say, for arguments sake, I can get a 990 Adventure with 30 000 km for a very low price from a friend in somerset west...
Can it be modified to meet the 990S spec?
And what needs to be changed?

 

[GeenSand]

 

[Roxtar]

 

[JacoM]

 

[chopperpilot]

 

[Noneking]