Back in the day of LPs, this was actually a question. LPs usually were about 35 to 45 minutes long, and an audio cassette about 90 minutes. So I usually taped my vinyl records on 90 minute cassettes (so I could play them in the care and for more convenient playing) and tried to group them in a way that made sense (to me).
I remember I had John Williams THE TOWERING INFERNO and EARTHQUAKE on one cassette.
Other "companion score" cassette tapes I had:
Goldsmith: ALIEN / OUTLAND Bernstein: THE MAGNIFICENT SEVEN / THE GREAT ESCAPE Bernstein: TO KILL A MOCKINGBIRD / WALK ON THE WILD SIDE (not a perfect match, but I had to make do with what I had... the better companion score to Mockingbird would be RAMBLING ROSE)
War of the Worlds and Minority Report is the consistent one for me.
One score I wish I had a companion for is Big Trouble in Little China, as I'm always in the mood for more of the same when I listen to it. Not a huge Carpenter fan otherwise however, and the other scores of his that I've tried don't hit the same marks. I'm sure there must be something out there, I just haven't explored that style of score enough.