Early Barracuda "Heavy Duty" Rear Seat Backs?

First a question: Are the rear seats all the same 64-66 Barracuda? Thank you.

Is the factory rear seat back fairly heavy (weight-wise) or am I just losing muscle tone in my old age? Carrying that thing around it's quite a chore for me these days. I read somewhere that old seats can become heavier with age as the foam "absorbs" who knows what. Thank you.

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Seat frame is the same 64-66, but 66 upholstery is different - seats and door panels. Edit: I should clarify that the REAR seat frame is the same. 66 front seats are different than 64-65 seats. Seat you have is 64-65. Here's a 66:

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Back seat in my 65 weighs 70 pounds. Bottom is pretty light, so most of the weight is in the back. Don't know about foam absorbing moisture, but I don't think the back seat has foam. Or not much, at least. But my back seat upholstery has never been off, so I could be wrong. At any rate, I'd guess most of the weight is in the metal frame, the chrome bar and the brackets for being able to fold it down.