|If you have a certified aircraft, go to the FAA RGL site (rgl.faa.gov) and navigate to Advisory Circular AC 20-138D. Section 6 of that AC contains the installation procedures for VFR GNSS equipment that has been accepted by TCCA.
As prescribed, have the system installed in accordance with the instructions in AC 20-138D, standard practices contained in AC 43.13 and in consideration of the manufactures instructions (if there are any) and have an AME sign it all off as conforming to those documents.
Make sure you have the prescribed placard.
CAR standard 571.06 has provisions to allow for use of AC 43.13 as "specified" data for this sort of installation. Some would argue that this is not a major mod and that "acceptable data" is sufficient. I would disagree. Read Appendix A of CAR standard 571.
You could alternatively get an STC for this. Major modifications need to conform to "approved" (STC) or "Specified" data. I don't think you need to go that far but you should check with your regional TCCA office to make sure they agree with your plan. Some disparity between the regions on how to interpret the CARs still exists.