firstlight, welcome to the Stovebolt. I'm not very informed about Canadian built trucks but you never know what a previous owner, or your granddad, may have switched along the years.
I'd double check the numbers and go from there. If its indeed a 235, or 228, then that is the engine to buy parts for.
There are other GMC members here that can help.
Since this is the Welcome Center I'd suggest posting questions in the best forum. Engine questions in the Engine Forum and driveline questions in the driveline forum and paint, well ask those in the paint and body forum.....You will get faster and more answers that way. Be sure to watch for your Canadian friends. They are here.