the wiring diagrams for the 8-track STEREO (420/R22) call them: CHANNEL "A" & CHANNEL "B"
& the speakers: LEFT - CENTER - RIGHT

the crossover is set for:
LEFT CHANNEL "B", CENTER CHANNEL "A", RIGHT CHANNEL "B"

what CHANNEL does a single rear speaker (426/R31) receive?

was there dual rear speakers available on a 1968-'70 b-body? what's the "SALES CODE" and/or the price?