Welcome to forums. Based on the 1/2 chrome fork and cottless crankset, combined with the steel rims, it would appear to be Centurion LeMans. The SunTour GT rear derailleur and the SunTour rear derailleur are the earlier style, dating it to circa 1976-1977, at the latest. Statistical probability would suggest peak boom era, circa 1972-1974. Centurion were rare in Canada, compared to the USA.

Serial numbers during this era were typically stamped on the seat tube. Both top and bottom locations have been reported, as well as sides and back. Regardless it probably won't help much, as the codes for this era have yet to be decrypted.

To narrow down the dates, I'd refer to the date codes on the back of the derailleurs. They should be a two alpha characters stamped inside a circle. See attached for sample of date PG (1973 July) on the back on a SunTour GT rear derailleur.

Link to OP's photos: https://www.bikeforums.net/g/user/536468