Considering that the spring on the automatic choke should just close it at 70 degrees F, you might need to readjust the coil on the thermostat a notch leaner (they tend to tighten with age). As the only way the choke coil can then "get heat" will be as eh heads warm the intake manifold, you might want to install a Edelbrock AFB, but then, TOO, you'll need an air cleaner to fit the larger mounting "circle" ('67 and prior had the smaller mounting circle on the carb and the air cleaner base), WITH an electric choke.
OR, you can be attentive to the car, after it's been parked for a while, by adding more throttle while starting. I believe the owner's manual mentioned 1/3 throttle, maybe 2/3 (?) when starting? Making sure the ignition is in good condition with some "modern" spark plugs (as NGK Iridium, or similar).
In fiberglass/foil item between the intake manifold and the valley pan is a factory item. Removing it allows air to flow under the intake, ala Edelbrock Performer RPM. I've heard TWO reasons for it. One is for better heat isolation of the intake form the engine. One is that it's there to help dampen harmonics which might occur in the valley pan as the engine runs, which might cause cracks in the valley pan's metal (with oil leaks?). Not sure.
Since "a smidge of RTV" was mentioned . . . what I usually do is get some black high-heat silicone-type sealer and put it into the beads on the bottom side of the metal, around the intake passages, where the manifold touches the cyl head. Smooth it out with a gasket scraper. Let it cure overnight. Then install as normal.
What this does is put an additional "seal" around each intake port, when the manifold is installed, which should better-ensure no intake manifold leaks. Plus the end/corners as mentioned.
Not a hard deal to do, but plan on a few hours, from my experiences.
Just some thoughts,
CBODY67
