What tracks offer the best left right separation?

Ortofon Record tracks 1-8   
Digital seperation is 3x LPs, ANY format.

The Ventures, serious seperation.

Electric ladyland
Jimi Hendrix, duh.

From the 1950's: any Phase 4. Total left, right back and forth. Music snobs almost universally hated the effects. A new medium, stereophonic sound, was being experimented with, for good and bad. Ever since Phase 4, the industry has steered away from such "gimmicks." Soundstage almost becomes defined as a requiring a center performer, but not with Phase 4. It will challenge systems because performers are often 100% left or right. 

a good album, lots of stereo fun:
Los Machucanbos

The best separation is in heavy metal or alternative music from 1988 to 2000 by the major bands also on vinyl it is the old command records or anything from fine recording studios in new york city.