Thanks for all the input, guys.
I'll be running it this way (Swedish campaign):
For the US; Only SF will have gotten weapons with rails and such (essentially what I've been staring at in those pics from 2001). The vast amount of line soldiers just had the "good ol' stuff".
For the USSR: No rails whatsoever, but Spetsnaz and such would have more N and M models of the AK, with options to mount their side mounted optics.
For Sweden: The AK-5C has been rushed into production due to not having budget cuts in the 90's, but it hasn't reached front lines really, but rather goes to the more "elite" units like Jägare and Specialförband.
In other words, the weapons *are* out there, but few and far between in working condition.
Of course, weapons like these would be prized possessions for anyone, so not only special units have them now, but rather whomever happens to have acquired one over the years (either from dead enemies, prisoners or from fallen comrades or just random corpses).
EDIT: As an added bonus for this, It'll be semi-easy for my players (all non military nerds) to spot soviet special forces due to them being the only ones using the newer black polymer furniture AK-74M's (not all of them have them, but they're the only ones who have them, essentially, in my game).
I would suggest that the weapons themselves aren't such a big deal, but the MODS would be... flashlight mounts can be jimmy-rigged with baling wire, but laser pointers and ACOG sights? Yeah, those would be worth quite a bit.
Since you're using Sweden as your setting, and since Sweden is off the beaten path, I would respectfully suggest that you read up on USMC Force Recon. Most of the Special Operators in 2nd MARDIV will come from there, rather than the SEALS. You could also say that an Army Special Forces Group is in the neighborhood... resistance warfare is right up their alley. I suggest that the 12th SFG[A] would be the logical choice. This was an Army Reserve Group similar to the 11th SFG[A] in the Ref's Book that consisted of retreads and part-timers that was oriented towards Europe in the 80s and '90s.