hummmm yea the 77 is close to stock. i have the heat tube and stove pipe intake for it but the egr valve is gone and the other vac/emmisions are gone. When i got the 77 the intire 4bbl linkage was missing and they had bent the stop tab on them to "open further????" but i made my own linkage and bent the tab and stiffin the spring and it seems to come on, sitting in park and hammer it she starts to open and road tested seems to work. Im sure that carb hasn't been opened up if ever but she starts runs and idles so well i can't emagine it needs a cleaning.
Ok, Lets forget about the EGr for now, the reason I mention the heat riser, and the Intake manifold exhaust crossover is because of the low temps you are operating in.
195* thermostat is really important.
The heat riser tube for the air cleaner, helps keep the incomming air at a more ideal tem, and the exhaust heat crossover runs under, and heats the area directly under the carb, to help with fuel atomization. Too cold, and the fuel comes out of suspension, and puddles,,which can cause a rich bog, amongst other wierd ****.
In my opinion, for your situation,,I would try to find a couple of TBI Air Cleaners.
Their diverter doors dont rely on a valved vacuum source to operate....which is helpful, if you dont have those vacuum lines anymore.
And just a side note, Stock GM manifold designs have a fuel distribution issue, especially to 1,3,7, and 8. Notice how the stock manifold T's out at those farthest cylinders. Aftermarket pieces have a nice smooth Y, which take care of this issue.