has anyone adapted a fold down rear seat into a car that didn't have one?

A friend of mine has a 71 Demon with old ratty bench seats. We just got a 74 Duster parts car with fresh bucket seat upholstery, but it has a fold down rear seat. We're looking for advice from anyone who has done it or seriously contemplated it.

What surprises would lurk if a person were to try to adapt the Duster fold down rear seat to fit the Demon? (the entire Duster is available for parts swapping)

Serious answers please :coffee2:
Thanks in advance!