carb choice and slick size

"AVS" is Air Valve Secondary. The secondaries are broken into two parts: the throttle plates and shaft, which is mechanical, not vacuum operated secondary; and the spring loaded plate that sits above them. When you floor it the secondary throttle plates slam open, but the spring controlled door above them doesn't. That air door lets the air speed come up smoothly so there is no need for a secondary accelerator pump and no chance of going over-rich when it's floored. Overall, it's a much better all around carb than a Holley, and will make the same power as a similarly sized Holley if both are properly tuned. But it will also idle cleaner and get better gas milage.
I run the Avenger series carbs too. They are great but again - will require tuning. Also - the 670 Avenger is a wet flow rated carb... So the direct comparison size-wize to a 670 Avenger would be the 750 AVS. IMO - a little large for what you're doing. I'd run the 570 Avenger on your car. If you go to a 3.91 gear or steeper, the 670 or 750 will get you better ETs. but with the mild gearing the smaller carb will produce better results.