Holley Street Avenger 670cfm to big for 318cui?

The area you may have difficulty with is the carb's circuit calibration.
If so, as long as you are willing to spend the time and energy, it can be recalibrated with some home shop work.

In my opinion potentially the MSD 6AL and distributor are going to be the bigger headaches.
Some of that is luck of the draw (quality)
The rest depends on what has been done to the engine.

If its a stock engine the issues will be:
The carb is likely to be rich at idle and take some effort to tune for good low speed.
Its going to be rich because it will have strong manifold vacuum. (Low MAP) with a stock cam etc.

The distributor issue will mostly be the advance curve. Chrysler engines like the two stage advance and the MSD distributors advances are really not good for creating an advance curve shaped like that.

my View attachment 1715732714

Just curious - if not the 6AL, what ignition do you recommend?