My 64 4 door is a 4 lug car. There is a post on this site some were that said the story is that early 64 cars with a 4 cyl or 6 cyl were 4 lug till they ran out of 4 lug parts. After that they were 5 lug.
All v8 cars were 5 lug in 64
I ran into trouble finding the correct front brake wheel cylinders fro my 64 4lug car till I bought them for a 63.