Which spacer is best?

So I'm contemplating running a carburetor spacer and have some questions. I have a 340 stock stroke , 10.5/1 , .525 solid cam with 1.6 RR , Eddy aluminum heads , Victor intake with a brawler 750 , 4 speed and 4.56s. I've had numerous people suggest a carb spacer. 1) Are they even worth it? Do they make a noticeable difference? 2) If so what spacer is good for my application? 4 hole? open? also height and material? Thank you in advance.