Here’s a link to an exploded view of your seat frame. The pin and keyhole that Spook is talking about are in the middle of the rail at part# 40 in the diagram. One pin under each rail and you will need to have both pins pulled back in their slots to be able to tip the seat up.

https://parts.volvocars.ca/a/Volvo_1992_960/_51956_5695695/Subframe-for-seat--electrical-adjustment/GR-65787.html

All kinds of others great parts views at that site so good idea to bookmark it.

Note that seat belt bolts usually call for Loctite so you may need a breaker bar to get them started.

Here are some general notes about working around SRS (airbag) components: Always disconnect and safely bag battery ground as noted by Spook and as well wait a good few minutes for the capacitors to fully discharge. Be aware that static electricity or arcing can trigger a discharge, so do not open electrical connectors until fully discharged and DO NOT ever probe with a meter! Any external damage beyond scratches to the control module or cable sheathing requires it to be replaced, especially important to note when wrestling heavy seats around. If a control module is ever dropped the motion sensors inside can get damaged, just like in a major accident. The OBD-I data link connector under the hood can be used to check and reset SRS trouble codes (see FAQ). Always be sure to keep your head out of the line of fire if an airbag should ever accidentally go off as a safe work habit. There’s nothing to greatly fear as long as you’re aware of the possibilities and are reasonably careful.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now