The analog gauge style oil pressure sending unit can best be described as a large bell, compared to the much smaller idiot light version.
1967 can be identified from 1968 and later by the way the wire connects on top. 1967 has a small disc on top, and a flat wire connector slides over it.
1968 and later versions both had a threaded stud on top. The under hood wire connector was a boot style connector that fit over the threads.
You didn't ask, but the water sending units have the same kind of electrical connections for 1967, and changed 1968 and later too.
Look for a picture of the reproductions, they look virtually the same.