1966-67 belvedere 1 2dr.post

I need to know if anyone knows witch car the roof on a 1966-67 Plymouth Belvedere1 2Dr.Post Sedan came from? The side panel behind the rear quarter window is longer,the whole roof is almost square.Belvedere1 was the base model,and they did'nt make very many,did they use the roof from another production car,maybe the A-Body?I know in 1966-67 Ford used the Falcon roof on there 2Dr.Post Fairlane sedan base. Hope someone can help.

A 2-door post car has the same roof as a 4-door car (top skin and C pillars) same rear window too.