I run into teh same thing, but if you call them, Tony has been very helpful getting p/n's.
One thing that drives me crazy is that you can't locate spark plugs for almost any of the Volvo cars. In the 240 blowups some years they are listed by Cam & Timing Components, other years by engine parts, and what they list in the on-line 4 plug kit is not the same as what's currently offered for $8, it's a different listing for $24.
Same for the '97 960, just try and locate them. You just gotta call them to find the right set.
I was looking today for a set for an '05 S60 n/a and went through every listing, they are not there. I only found them by going to the FCPGroton website looking up the p/n and the Tasca listing is there, but no associated with any car year or model or catalog listing. You figure spark plugs should be right up front in engine maintenance section, but they are not. This bugs me.