All Classified forums require a Site Supporter subscription. It is only $25 per year and you can buy and sell whatever you like on the forum. To become a Site Supporter, go to Your Profile and select "Paid Subscriptions."
I think he is asking whether pre-1984 bench seat frames and mounts are the same as (or similar enough to) 1984 and later bench seat frames and mounts, such that the earlier seats can be easily upgraded with later model cushions, upholstery, and through-cushion seat belts.