All comes down to your fuel delivery needs GPH and tune ability for your application. Personally, I have a RSA-5 on my Blown IO-540. I'm maxed out @ 25.4 GPH. Planning to go to a RSA-10 when I find the time to fab up a new intake pipe for the blower. If I'm not able to fine-tune this unit, I'll already have spoke with Don @ Airflow Performance to purchase a FM400 servo. A little more tunable unit for my existing fuel system app.
Thomas S. www.g3ignition.com