In my ongoing search for retractables, I've come across rear belts from a 960 on ebay for not a lot of money. As I've not had retractables, I don't really know what to look for as far as will they work/bolt in. The ebay item numbers are:
seat belt-1807239551; seat belt locks-1807239986. Sorry I don't have the URLs.

Does it seem reasonable that the belt mechanism could mount on the pilar, up high and the other, fixed end could mount low, and the latch could just replace the current latch between the seats?
Originally I thought the reverse, but noticed that there is a plastic rivet or somesuch on the belt to keep latch from sliding down the belt - if installation was inverted, (retractor on the floor and fixed point up high) the latch would always be down near the floor. Is this making sense?
I don't know if belt lengths would be different, as in these could be too short. They look like they should be long enough, but I don't know. Anybody out there tried this. It could be a simple, inexpensive upgrade, for all of us in pre-retractable cars! thanks