Its going to cost you less money to have a GOOD rebuilder rebuild that quadrajet than it would to buy any new carburetor. If you didn't have a carburetor already, it might be a different story, but a quality rebuild of the stock carb is going to get you the best performance and probably be cheaper all the way around.
Cliff's High performance would be my recommendation. Cliff literally wrote the book on quadrajets and they will rebuild yours or sell you a custom matched rebuild kit if you want to do the work yourself.
https://cliffshighperformance.com/services