A couple of tips for the next person who has to pull the instrument cluster from a 93 940 base non-turbo wagon.

The cluster from a 960 will fit, all part/PCB numbers & connections match. And it has the ambient temperature display unit if you care to add the sensor later on.
Unfortunately, I can't tell what year 960, because the cluster I bought was pulled from a 1994 940.

The cluster trim ring is held in with 2 spring clips, one on each side.
I used a dental pick with a hooked end to pull the left side of the trim as I pushed on the clip. Didn't even have to mess with the righthand clip.

The spring clips are actually fastened to the dashboard, through the potmetal cluster holder. In my case, the dashboard had broken at the connection points, so there was nothing for the clip's screws to grip. I use flat "speed nuts" to bridge the gap left in the broken dash opening, similar to these -
http://www.lowes.com/lowes/lkn?action=productDetail&productId=139274-37672-881231&lpage=none

Thanks to the FAQ section on 900 speedo/cluster repairs ... and to those who answered my questions here.