NOS carburetors. What issues to be aware of if any?

I would pull it apart to check out the condition of the insides anyway.
And also to make sure that the float is adjusted properly etc. and it is clean and everything is there.
If you have any doubts, replace parts as needed.
Keep in mind that a lot of N.O.S. parts were not put on cars when they were new because of some minor defect.
This is especially true with body panels.
Also, I think that they are asking top dollar at $269 for a relatively uncommon application........
What is the difference in this carb and the one that they are asking more for?