I don't know about '83 but on '85 911 the Boge strut (black I think.) is 'disassebled' and the guts/fluid of the strut removed.
Make sure you know the color, this probably won't work unless they are Boge struts. Koni and Bilstein are different color. Boge was standard issue.
Important: The lower portion of the strut does not need to be removed from the spindle assembly on the 1985 (not sure on '83).
Support car, raise spindle assemble from below to compress strut. Remove locking washer and nut with appropriate tools (something must hold the plate). Remove nut/washer and lower spindle. I used ~7/8" (?) with 3/8" breaker bar. If rod is too long compress by hand (hard).
After removing the nut in the trunk, the rod coming from the top can clear the fender and pull it out ~45 degrees. Watch brake plumbing though.
Removing top with channel lock pliers. Gas will be released as it's under pressure. Get rid of all fluid per Bilstien.
Bilstiens in this 1985 application are inserts that screw into Boge case. The supplier should provide a Bilstien tool pictured in this post.
I spoke to Bilstein on Sport vs Non. They strongly recommended Non-Sport even for my heavier Cab. "unless" the car was lowered. I think it has something to do with operating range.
I pulled the top of strut out and checked the tightness of the original Boge to prepare for this project. I reinserted into car without needing alignment as the rubber attach at the top was not moved and of course the bottom portion wasn't either.
Oh yes, mine rear would do a little dance on the highway before the rear shocks were changed.