67 slant with 1920 holley dies when engine heats up and choke opens.
Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted
here for free download.
That "extra threaded hole" on your replacement carb means it is a '69 unit (unless it made a voyage down from Canada, where the '69-only-in-USA throttle plate
anti-ice system was available starting in '61). The carb is calibrated for that air inlet at the throttle base to be open and flowing; it's best if it's routed via a screw-in hose nipple to the clean side of the air cleaner, but that might be more work than you're up for.