I don't know many people with built carb'd engines without exhaust crossover trying to drive them in sub-freezing temps. I do it but most people here in the states put their muscle cars away for the winter and only drive them in warmer weather.
Our winters can see 85 F here. Even back in Oklahoma it wouldn't be unusual to wear shorts on Thanksgiving or Christmas but the next day it's -14F windchill.
Wonder if the OP could rig up a dual snorkel air cleaner with 2 heat risers?