I have a 3"x14" K&N round drop base air filter in place now and was thinking of trying a 2.25"x14" to make room for a 1/2 open carb spacer. Do you think the reduced surface area of the air cleaner will make any noticeable difference when running on the street? At the track I pull the filter so it won't make any difference there.

Wont be any different... your at part throttle MOST
of the time

I'd be way more worried about top of carb to lid area than element area.

Try them both back to back(with cool down in between)at the track and see for yourself.
As stated,on the street it won't make a bit of difference in normal driving.

Quote "For performance applications, you should shoot for a pressure loss in the 0.5% to 1.0% range at the peak power rpm. Less is
better".

http://www.secondstrike.com/Technical/AirCleanerHelp.pdf

Page 4 PDF or page 20 article "Typical Results"

Warning ford related but it may give you some info on air cleaners.