1965 273 carb?
Ok here is the deal.
All 64/5 V8 2bbl have the same heads and intake.
66-69 273 are the same. 66-69 273 heads you can use any LA series intake 66 and up.
You can make a modification for 64/5's to take the later intakes but it invovles wollerin out intake bolt holes and such, I don't recommend it.
If the car is all stock going to be a show winner take the time and find the right part.... If its a cruiser or rat rod, put later model heads on it and put whatever kind of intake on it ya like.
Little hint, anything 64/5 is treated like gold, you are gonna pay for it.
Your linkage should be plug and play, when I had my Holly 500 2bbl on my 273 I had no modifications to make.