jr

Rob, you're pretty close to mine. I have 68 primaries, and 72 secondaries.

Does, any one know if the jets on an Edelbrock carb translates back to the same as a Holley? Is 68 holley the same as a 68 edelbrock?

Griff

jr, what I'm saying is that the opening of the secondaries on a carb with MECHANICAL secondaries is controlled strictly by how far you push the throttle open. They will open at "X" throttle position weather you have a light load, heavy load or no load on the engine.
You have to be able to get to WOT before you can determine if you need more or less prop. If you put a bigger prop on, the secondaries will open at the same throttle position. The rpms will be lower and the engine will be working harder, but the throttle will be in the same position. You don't want to "lug" the engine with a bigger prop.
At 3/4 throttle and 4500rpms, I think you are probably in the ball park with the prop. You won't know for sure until you can get to WOT. Also, if you are lean, you definately don't want to run a bigger prop. The engine will have to work even harder and will lean out even more.

I wouldn't do any comparisons between Edlebrock jet sizes and your Holley. They are apples and oranges.