I don't think it is possible to make a 0w-30/0w-40 strictly from a group III basestock - the extremely low temp viscometrics just aren't good enough. The Petro Canada 0w-30 also contains some PAO and most of these grades are PAO/Ester blended basestocks.
Chevron offers many different products in their Delo 400 line. I would imagine 15w40 to be their most popular, but they also offer a 10w30, SAE 10, 20, 30, 40, 50, and two synthetics, as TooSlick pointed out, which are 5w40 and 0w30.