I'd say it's from a four door, it has the large rounded corners for easy access.
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If it's of any help my 59 Dodge 4 door has the rounded end seat bases and doesn't have any " dips " in the top of the seat back in the middle either.
Seems like the 2 doors have the dips in the seat back in the middle.
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What dips are you talking about ????
Ahh ... thanks Buddy, i thought i found a seat to buy but it didn't have the dips in it .... Rats ..... so i guess i will keep on looking