What tracks offer the best left right separation?

Separation is not a part of live music as, unless you're lying face up on the stage, blend is what live music is about. Even in situations with minimal or zero sound reinforcement you're not erecting a wall between instruments (except the plexiglass barriers here and there). I've mixed decades of live shows for money (yes, I'm a mix slut) and the only thing I put in stereo is  sometimes a tiny bit of stereo reverb which fools the audience into thinking they're having more fun.  Otherwise the art of panning things together in recordings is what gets the mojo happening.

Try Yello.

Another +vote for 'Yello'

Happy Listening!

Most old Allman Brothers have a different Drummer in each speaker.

There were recordings of trains going from one side to another back in the old days.  Try one of them, maybe.

Cheers!