Air Impact tool rec?

[Douglas Shook <dshook@usc.edu>]

Shop Talkers,

I have a "Heavy Duty" 1/2" drive air impact wrench that doesn't have
enough torque to break the lug nuts loose on my old 1975 Ford E250.  I
break them loose by hand and then run them off with the wrench--really
"heavy duty," no?

Does anybody have a recommendation for a good 1/2" drive air wrench? 
I'm willing to spend whatever it takes so I can throw the one I have
into the street in front of the garbage truck...

thanks,

doug