Just a handful of thoughts from a "former" AM guy of 20 years. :) (It's still in my blood, tho!)
I wouldn't decrease the high end bandwidth like that. It helps with speech clarity to keep those highs out to 9KHz or so. There really isn't much "power" in the highs, either. Depending upon the radio, those highs will help with intelligibility.
You COULD reduce the low end a few DB, tho. THAT is where POWER is really wasted, considering that the VAST MAJORITY of AM listening isn't done on hi-fi systems with big woofers. ;) Anything below ~50Hz, for example, is really unnecessary for talk formats. A slope-off, rather than a brickwall, is good. Too much bass makes talk sound too muddy.