The '67 hood is dimensionally the same as the '68 and '69 hoods. The hood latch mechanism is different on '67. If you install a '67 hood on a '68 or '69 vehicle, you will have to modify the hood latch mechanism. I don't know what this requires. Most of these types of questions concern installing a later '68-'69 hood on a '67. That is a fairly easy fix - install the later hood latch assy.
As far as gaps, they should be as even all the way around as possible. Not sure of specific measurements, but someone here can give you a good idea.
