If you want to change all to factory aircon, that is quite a job. Many parts are the same in the E32 and E34.
Best is you use the online parts catalog and compare the models.
I would just leave it if it works.
Here are some info which might be helpful for the change if you still want to do it:
IHKA components
There are more infos on Johan's page such as replacement of the aircon parts for 134a, and also look under center vents. If you want to do that job, it will look this this some day.