I sometimes wondered that myself, until I sat down and really watched the sequence. Then I saw it wasn't possibly shot during Part I, for the following reasons:

1) Carlo was fatter in the face - in Part I he was in good shape.

2) Connie's hair was too styled - much like her hair in II than in I.

3) Sonny's hair was too natty - obviously he had a special "style" done for his role in Part I, but couldn't get it the same for Part II.

4) Tom's hairpiece was "obvious" in this sequence, whereas in Part I it wasn't that noticable.