Yes.
No
with the exception of the bumpers & bumper brackets they are identical
Yes. The only difference besides the inside door panel is the 73-74 doesn't have the wing vent window like the 68 -72.
Yes.
where are the holes located in the roof of a 1972 chevy nova for seat belt installation
No
No.
If it is the same bodystyle, yes
Yes it will bolt right on.
8.5.
Yes
Not without modification. The 1973 and 1974 body styles are unique in the Nova series.