Getting a manifold machined for carb bore/butterfly clearance will either be: a guy with a die grinder and carbide burr, or it's going to be expensive.
Machine shops are likely $100 minimum to do that unless they happen to have a fixture for that intake laying around.
Trans-Dapt used to sell an adapter to put the newer/larger Eddy onto an older AFB manifold. Don't know if they still make it.
If you get an OEM or aluminum intake it will likely be sized for 360 ports, and you should get one with smaller 318 ports.
Otherwise you'll have a bigger intake runner feeding into a smaller cyl head port. Guys do it all the time but it's not good for smooth airflow.
I don't know if an OEM 318-4 intake with small runners was ever made?
Aftermarket ones exist, but you'll need to scour for them.
I wouldn't fool around with spending $150 for a 60-year-old carb, who knows if the throttle shaft bushings will be good, rebuilding it, etc.
Buy a 500-600 Eddy AFB or AVS with electric choke, bolt it on and go driving.
Trying to hook an OEM divorced choke up to an Eddy carb isn't as easy as it seems it should be. BTDT. Hence why I recommended an elec choke.
Although you will need a 5-1/8" air cleaner to go the Eddy route.
To go teh 273-carb'd route, you'll need a 4-1/2" air cleaner, and that will either be an unsilenced unit from a 383HP, or a single/twin snorkel from a 383, or a 70s version from 360 or 400-2.
An interesting combination for Eddy carbs is to get an unsilenced Slant 6 air cleaner lid, and an aftermarket 10" chrome air cleaner with 5-1/8" neck, and use the base with the 6cyl lid. The 4-barrel unsilenced air cleaners (like in the picture) are getting scarce and pricey, the 6cyl versions not so much.
If you want to go this route, I have a couple of powdercoated 6cyl lids, I could sell you one.
If the Trans-Dapt adapter interests you, I might still have one of those left.
