If you read the declassified sections of Star Wars it seems pretty clear that particle beams (be them charged or neutral), lasers, x-ray bomb-pumped lasers, and so forth were all on a time horizon for the 21st century.
On the other hand ground based weapons plus orbiting Brilliant Pebbles would be eminently feasible (the ground based stuff, actually, would have been doable in the late '50s—see MKSheppard's The Big One timeline elsewhere for technical detail) and it wouldn't have been too much work for stuff for Project Thor.
So, yeah, I'll shoot holes in the energy weapons but Brilliant Pebbles would suffice for your needs. You're certainly not going to put an energy weapon in the F-23, though. (Ooh, do we get a naval F-23 to replace the F-14 instead of the lousy Super Hornet?)
If you want to save the USSR in some form beyond a broken down Gibson Neuromancer style shell, they really need a lot of work. I'm not sure they could be saved, starting in 1979, but 1987 is certainly too late.