Your friend moving to Missisauga will not have any problem whatsoever.
There will be no modification of any kind required on the car. The speedo will not have to be replaced. The only problem will be that the car will be very slow. Everybody will be doing 120 while he'll be going only 60.
he may be required to go through a safety inspection before registration, but it is a standard practice in Ontario for all cars at a certain age (not sure about 1998). The safety check is basically lights, brakes, steering and the like. There will be no problem with pollution matters as both the US and Canada have standardized their requirements.
Canada say welcome to your friend.