FYI could not locate anything in Canada. Standard CTS tank does not work. $1400 from GM. I know there are forum vendors who will sell GM parts much cheaper than our local dealers but I ended up locating a tank in Minnesota from a wrecker for $300 so I am guessing this is the way to go.
Got the tank from the wrecker to Edmonton for another $290 through UPS so about $600 total. Tank is however, no good, Will see if I can get any money back from the wrecker. On the positive side I googled genuine GM parts and found a few different OEM suppliers from the US who will ship here. Should have the fresh tank here for about $700 CDN which is barely more than the used one. Should have done this to start
Final outcome. My two tanks including shipping cost me $1400 less install labor which is what a CDN tank would have run in the first place. However, it turns out that only the 04-05 cars use a different part # for the LS6 vs V6 cars. All 06+ use the same p# as the 04-05 six banger which probably means I could have used any 6 cylinder CTS tank from a local wrecker and saved all the hassle. Unless there was some kind of change around the fuel tank area from 05 to 06 in the Vs which seems iffy.