That would support my theory the spacers were only on the B-bodies, maybe only the Charger? I know I've seen a couple other B's with 6-ways (a RR and a GTX) but I've no idea whether the same braces were used.
The Roadrunners/GTX/Sats also have the spacers. The E bodies have the seat reinforcement plate on the underside of car so the spacer isn't needed and the b-bodies with bucket seats have the reinforcement plate top side under the carpet, reason for spacer.
