I think how the new rules read you can do it, but the engine has to have all the emissions devices for the year of the engine. It (engine) also may have to be stock with stock intake, FI, etc.
You would have to research and know exactly what you can do before starting the project.
Also be aware that your car may be considered a "hot rod" and I'd definetly check how that will affect your insurance.
https://www.ontario.ca/faq/do-hot-rods-need-drive-clean-test
Of course if you need any help on your projects I'm real close to Oshawa.
I've rebuilt a G50 (and 901,911,915,930) and I converted my '67 bug to a 911 (901) transmission. So I have a good idea any way you decide to go.