I would agree with a lot of things that have been said here about hot rods/cars in the sixties. I really didn't know anyone putting any money or work into a 4 door. Back then it was affordable to get a 2 door to work on and drive. As far as sales go the 4 door versions pretty much always outsold the 2 door versions. Most of my friends' parents would by 4 door versions including my dad. The T-Birds he had were 2 doors but they were the exception. With the cost of Barracudas, Challengers, Road Runners, Super Bs, etc. I can see why some guys would go with a 4 door version. In the late nineties I had a 4 door 57 Belvedere that I used as a daily driver. The engine was shot and I bought it for next to nothing for parts. I ended up putting a 318 with a 904 behind it and drove it for years before I sold it. I think it is less a trend and more like the only affordable option for some models.