Difference between doors from a 49 to a 54?

[Matt300ZXT]

The guy I got my 54 from gave me a couple really good condition doors from his 49, which he chopped the cab to put it on a VW Bug frame, and said I could have the doors. I've been checking out some vendors online and they say door shells are for like 47-50, then like 51-55 or something like that. So they say a door from a 49 isn't supposed to fit on a 54. Any idea what the difference is? I'd prefer to use the much better condition doors if I could and give him my doors to chop and re-size for his project.