I know this is heresy on this site, but unless it is a crazy camshaft, you should be able to get a Holley 600 (I might go 650 cfm if I was buying new) to run as well as Fuel Injection on a motor like this. It might get lower mileage and will be questionable on a sniffer test and never pass a visual test, but the right tweaking will do wonders. If you were wondering about the visual test, the extra 2 to 4 cylinders will give it away.
I have had carbs that were the only thing to start when it was way too dang cold to go outside, and my current carb car fires up quicker than the F.I. vehicles we have.
When you first described your issue, I wondered "Does it have electric choke or a manual/cable choke?" There are two adjustments in this system. One controls how far closed the big choke flap is. That is run by the cable or round electric thing on the passenger side. The other is the high idle adjustment screw and cam. It is adjusted by a screw that you only get to from underneath with the throttle open. Get them balanced right (and get enough gas from the accelerator pump to start with) and it will purr right off the bat and stay at a good high idle speed until the choke gets hot or until you back the cable off.
Speaking of the electric choke coil assembly, MAKE SURE it has a strong 12v wire that is switched with the ignition. But do not use the wire from the ignition coil. Some ignition supply wires have resistors or resistor wire to protect the points. Then the choke coil is sluggish that way and will not get hot at the right time. Then the choke stays on, the secondary side may not open, and you are running rich all the time.
For the rest of the tuning, I would have to know if it is a double pumper or a vacuum secondary, and the Holley books will cover all that until your head spins. They will cover jets and power valves and the air bleeds, most of which should be close for the size of the motor and carb out of the box. But you never know what the last owner did. If you have a Vac. Secondary carb, the quick change kits for the secondary springs are worth EVERY penny. Do it once and you will agree.
THIS IS MY REQUEST FOR RELATED HELP, PLEASE. One other tuning thing I have never run into is a chart of what the colored accelerator pump cam fuel curves actually look like. So if you find a good graph, or a description of what each color is supposed to do, please post and credit where it comes from. On a hill with a full car, it leans out under initial tip in. It is not enough to ever notice with one person in the car. Otherwise, I just have to guess and test. I just want a little more fuel under part throttle when my car is loaded (and the driver is not of course).
You are right about Mad Mike being a bad influence on you, but flushing the tank will not hurt, especially if you are already in the area. He sets a heck of an example of how to do it right.