Cam break in during cold weather?

IMHO, that 5W at 35F is gonna be a bit thicker than 10W at 50F. I'd probably put a milkhouse heater under the engine and a wind block under the car and let things get as warm as I could. iMHO, it is just a matter of getting good oil flow right away.

And if you have the stock valve springs, the issues tend to go way down anyway.