Having DRIVEN my Duster in 40-degree temperatures with an electric-choke AVS, Air Gap intake, no heat riser, and an open scoop, just...don't worry about it. Pump it once, crank and fire. Mine being a 4-speed, I run it 1-2 minutes to stabilize the idle and go; drive gently until the temp gauge is past 125.
my old 5th ave was cranky and didn't like to start when temps got under 20 with an air gap and 600 electric choke edlebrock carb.....will F/M/J exhaust manifolds fit? they might be easier to find with a heat stove than a 55 year old A body one.....