new carburetor

500 cfm is plenty. The stock 4100 carb was something like 420cfm. When you get too big with a stock motor you will wind up with less throttle response. 500 cfm, though, should not be too much.

There are no carbs "set up" out of the box for your engine. So you might as well get that out of your head now. The pieced together carb could very well be tuned for it though, if the tuner knew his ****. Being as you've posted this, it's pretty clear to me you don't know a whole lot about the subject. Spend some time to learn your Holley and you'll come out way ahead of those who just toss out good parts in a vain search for the right combination. You just may also save a bunch of money too.

The power valve should be a 6.5. Jets should also be right, usually 64's to 68's. For a stock motor, leave the accellerator pump and squirters as is, just make sure there's no slack in the pump linkage. It should start to squirt as soon as the throttle moves. You can lighten up on the secondary spring to the lightest to next to lightest, the brown or black spring a 600 comes with won't let it open till about 4000-5000 rpms. Other than the secondary spring, a Holley 600 out of the box (list 1850 or 80457) is dead on right for a 302. The only other thing I like to do with one is swap the bowls for center hung/dual feed, it doesn't run any better, other than maybe cornering, but it improves the looks in my opinion. Taken out of the box, the only thing that needs to be done is set the idle, idle mixture and pump arm clearance. I also remove every piece of the choke assembly, I don't need it where I'm at.