Has anyone used the Daytona carb on their slant 6?

It's getting hard to find really good carbs especially for the pre-'67 rotating-rod type throttle linkage setup. That Daytona carb is not a "direct replacement". It requires a fair bit of adaptation. It's from Argentina, a copy of a local Argentinian Holley 1922 carb. They can be made to run passably well. Current-day "remanufactured" carburetors are junk, almost without exception. Older rebuilds are much better, and new old stock is best.

In your position I'd probably buy this in preference to the Argentinian carb.