I'd forgotten about that - I think I mentioned this elsewhere, but all the King Biscuit Flower Hour quad masters burned up in a warehouse fire in the early 80's, so the conversions that exist are probably as close as anyone's going to get to the quad mix. As far as I know, KBFH only ever sent out SQ-encoded reels so the discrete 4 channel master that perished in the fire was probably the only copy anywhere. All the modern-day re-releases of KBFH material is newly mixed from the multitracks, which (some years later) the current rights holders discovered were stored independently from the mixed masters.