You car do as you like.
BUT....
my friend has a 67 dart with 68 hood with Dodge script and 68 fender top turn signal and side markers on the front fenders only.
Looks fine but he gets a lot of comments like is that a 68 or a 67 and those are wrong for a 67, etc.
He jokes that it's a 67 1/2
So if you can take the heat and don't mind the constant questioned looks on people's faces, drill away.
Personally if it's a 67 leave it a 67.
67 was the best year for all 3 A bodies IMHO