With the seeming abundance of speed density systems out there, I'm not sure how many folks will be willing to sacrifice some airflow potential for the benefits of a mass airflow system.
Actually having a measured quantity of air mass entering an engine is, however, more accurate than depending on calculated fuel tables, and it's nice for the end user not having to dyno tune the system when changes are made to the set-up. I do realize some of the newer SD systems are also capable of self tuning.
Interestingly, although Pro-M only rates their throttle body at 1000 CFM, Accufab (whom actually manufactures the Pro-M bodies) rates the same 1-3/4" butterfly throttle bodies at 1215 CFM.
I don't have hard numbers (airflow vs. pressure drop) but have read the on throttle body MAF flows 1000CFM. I do know that it is an 85mm opening (less of course the center bridge) and I specifically asked how much horsepower it was capable of supporting. I've been told the single configuration (Pro-M also has a dual set-up for higher powered apps) is good to about 700 HP.
I had originally intended to use a carb hat and cold air tubing to pipe to a fender mounted MAF. I abandoned that idea since my research has pointed me to believe that a carb hat is heavily detrimental to naturally aspirated power levels. Surprisingly, I figured the big problem would be poor distribution to the short side radius cylinders, but in actuality it appears that restricted airflow is the culprit. Again, I have no hard numbers, just what information I have been able to eek out from various internet searches.
I found an air cleaner that fits the Pro-M throttle body perfectly, clears the throttle linkage, and IAC motor quite handily, and I think it even looks real nice. Stupid cheap as well. I will be getting the MAF early next week and will post some pics of how it interfaces with the air cleaner. Bottom plate of this cleaner has a 1'' "hump" in it all the way around but the filter base is at the carb flange height, so it's just a shade taller than the height of the filter element.
Edit: I just did what one does when they assume too much, I truly have no knowledge of whom actually manufactures the Pro-M billet TB.