71 Duster Stock Buckets?

When I was removing my seats I noticed that one of the bolts was smaller in OD than the others, was a different style. I'm not sure if I'm going to order new covers/cushions or see about a custom upholstery job, but if I go to order I want to make sure these are Duster seats and if it matters if they are correct year. They do match the rear seats/door panels, it's just that hardware has got me wondering. Thanks if you can field a newbie question.

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