Well, you will find some 0w30 and 5w30 dual rated oils up here, as you alluded to. Of course, none of them will be GF-4 or GF-5 rated, so don't have quite the same limitations that an SM/GF-4 or SN/GF-5 PCMO would have.
At least for a time, a lot of PCMOs were dual rated, at least with obsolete Cx specifications. I noticed a lot of the PCMOs are no longer dual rated, forgoing the old diesel specifications.
Check at
http://imperialoil.ca/Canada-English/Files/Products_Lubes/IOCAENCVLESEsso_Xd-3_extra.pdf for a few interesting HDEO grades. The lines are being consolidated with the Delvac ones, so not all are/will be available.
I'm going to try to get some of the 5w30 SH/CG-4 for my old F-150. It'll have plenty of zinc and not be outrageously thick. Last time I checked, though, they wanted too much money for what is essentially an outdated and discontinued oil.
To the original poster, I tended to use 15w40 in my 1991 Audi 200 Turbo. It was the most widely recommended grade in the manual, and it's pretty hard, if not impossible, to find a 15w40 that doesn't have a C rating in addition to the S.