Bucket seat swap

There is a set of bucket seats on ebay that are out of a 73 Cuda. Can the frames be refoamed and reupolstered to replace the factory seats in a 70 340 Swinger? These have the upolstered back as opposed to the solid plastic seat back on the Swinger.
My understanding per my upholstery shop is no they can't because the 72+ don't have springs attached to the back frame, there is piano wire embedded in the foam instead. And it didn't sound like the foam can be cut and molded to accept the 70 legendary fabric. I haven't checked any other shops, just figured I would eventually find the right seats or pony up and buy repop frames when the time comes.