Worthwhile Canadian Initiative – aka Prof. Gordon found data in the 2001 Census Handbook pp. 29-34 that did a great comparison of census questions between 1871 and 2001 and then added 2006. His analysis and the table are very enlightening!
This blog post Census Questionnaires – They’ve been long for a long time! has links to almost all of the questionnaires / schedules since the BNA Act of 1867.