This is from RIV website, under Vehicle admissibility.
"Please Note: Neither Transport Canada nor the Registrar of Imported Vehicles (RIV) can guarantee the accuracy of the information contained in this list. The information is subject to change without notice.
Vehicles that have been modified from their original state, other than regular maintenance, may not be eligible for importation into Canada.
For example, a van transformed into a motorhome (often known as Class B motorhome), a van equipped with raised roof and/or modified interior, a pick-up or a passenger car equipped with lift kit
, a motorcycle converted to a motor tricycle (trike), etc. This also applies to Canadian vehicles modified in the U.S. and returning to Canada"