4 bbl Carb bases come in two basic designs. Spread Bore, with large secondaries and smaller primaries, and Square Bore, having both primary and secondary butterflies approximately the same size.

These should work for your Edelbrock. I'll leave the choice between open center and square bore to you. Either will work with a square bore carb, but the open one will work with both types of carbs unless you have huge secondaries, like in a Holley 850. Even then, a little judicious work with a Dremel with do the trick.

http://www.summitracing.com/search/p...etor%20Spacers