My car is Canadian too, moved it from Toronto to California 3 years ago. I had a KPH speedometer up until I moved here when I swapped the face plate with a junkyard salvage from an El Camino. So that code doesn't reference the Canadian speedometer, good thought though.
Doesn't make a whole lot of sense that it would read in MPH, the only difference with the stock speedos between US and Canada was the face plate on them. Sounds like yours needs calibration.
You should be throwing Trouble Code 24 if you didn't have a VSS. I just checked the parameters for the '87 SS ECM and that code is definitely active.
Your air/fuel mix is going to be whacked without an O2 sensor. How are you passing Ontario emissions even? The computer uses the info from the O2 sensor to control the mixture control solenoid in the carb. You really need one of those put into your headers.