what temp t-stat?
Got access to a thermal heat gun?
How hot is the bottom tank compared the the top? Are the cores of the radiator hot all the way across?
Does the temp go down if you turn the interior heat on high? (heater core is just a small radiator).
When at 230 does the air the fan is pulling while the engine running feel hot?

I feel that even if your timing was off, that at 35-45 degrees ambient there should be enough heat exchange for it to run normal "IF" the radiator is flowing.

What's the condition of the coolant?
Has it ever been brown/rusty?

Not sure how it is up there, but finding a radiator shop is near to impossible anymore.