Ahh, yes. Recoil pads. The Achilles Heel of Sakos.
The rubber formulation in old Sako pads was apparently very inconsistent. I assume that the pads came from a suppllier rather than being made by Sako. At any rate, some of the simply turned to soft mush, while others became hard and brittle. If you are lucky, you have one with the "right" rubber formulation (don't know if this is the right amount of sulfur, curing, or what) and it has stayed healthy for the last 40 or so years.
As I have lamented here on this site before, it seems that there would be a huge market for high-quality Sako reproduction pads and someone would take advantage of it.
At any rate, the old Sako pads, as Mike alludes, were glued to the hard black rubber (or plastic) base that looks like a "black line spacer" between the pad and the stock. If you want to remove the entire assembly, it should come off with a screwdriver. I don't know, but would expect pads for the Vixen and Forrester Deluxes to be the same dimensions, just as are butt plates for the standards and mannlichers.. Of course, there were no butt plates, only pads, on the Finnbears, and I'm guessing that their pad is a little larger than those for the smaller actions.
Bottom line: There is a chance that you could remove the pad from said Vixen and reinstall it successfully on another Vixen or Forrester stock. But as hayseed says, these were most likely hand-done and could vary slightly in dimensions. Also, the value of the stock from which you removed it would be significantly reduced, so you might find the excersize somewhat expensive. I think I would simply have a professional install a nice looking aftermarket pad. Knowing what I do about Sako pads, I never discount a gun due to having a professionally installed replacement. I do give a gun a little extra value if it has a well-preserved original pad.
Next: Front sight hoods