Mine was done in London Ontario and came out great ! Hopefully there is someone in Western Canada for you.

Port Moody radiator
Couple of old school guys still doing great work

Yes, and if you have transmission coolant lines running into the rad you will really want to make sure all is 100% leak proof. Transmission fluid & coolant don't mix and it will quickly destroy an automatic internally.

Are there any Canadian radiator core manufacturers left? Here in Australia we still have a couple who make brass cores.

When I bought my 68 Grande Parisienne out of Winnipeg, I asked the owner to put the original radiator in the trunk when the car was shipped to Australia. He seemed perplexed that someone would want that over the Chinese made "Champion" aluminium radiator he'd fit when he rebuilt the engine. I was perplexed as to why someone would cut & reroute the transmission lines and trim the original fan shroud to fit a cheap alloy radiator that looked completely out of place in the engine bay.

I'm half way through rebuilding it now. I own and operate a radiator repair shop and would be more than happy to help out, but I'd reckon shipping to Australia and back might just blow the budget. I hope you can find someone local to do it for you.