This is a good question.
I know you see the general statements on Killer Ron's web site:
Quote:
The 1475 CFM (2-1/8" Butterfly) TERMINATOR SYSTEM is utilized on engines ranging from 355 cubic inches up to 502.
The 2100 CFM (2-1/2" Butterfly) TERMINATOR SYSTEM has became very prevalent due to the increasing cubic inch and higher horsepower engines being utilized. This system has a wide range of uses from healthy small blocks to 632" Big Chief and Big Duke Engines.
My opinion:
The 2100 CFM will work the same, no down side. The 1475 will work the same, but if you try to go much over 950+ hp it might limit things.
FWIW, my mild Indy 440-1, 511 CID has a 1800 CFM Flying Toilet and works just fine, footbrake and all. I don't need all that airflow, but it doesn't hurt on an injection system for drag racing. 
Either way, I think they will set you up with a 0-1/2 pump. Right now Ron's is cutting the price by supplying a gold vane pump (like I have) instead of the more expensive gear pump. But I think the couple hundred more for the gear pump will be a better value over several years (durability). Ask them about this, I have no complaints about my gold vane pump.
This site has a bunch of injection users. Check there. This post isn't exactly your question, but is related. DRR forum 
