The last seats I made this mod to were out of a late '60s Rambler. On them it was just a case of pull out one bolt, remove the stop and throw it away. They were identical to the folding variety except there was an extra piece bolted to the bracket to keep them from folding forward. Since they (being out of a Rambler) were recliners they were already hinged, and it was a no brainer for Rambler to use the same parts with only a minor mod to keep them from folding forward.

I was hoping that Chevrolet would have as much sense as American Motors and do something simple like that. I'll probably have to drive out there and look at them. Maybe I can see how they work without a lot of disassembly.

Don't lose your head to save a minute,
You need your head, your brains are in it.
Burma-Shave (1947)