I haven't found the turret ring diameter of the LAV-25 (but I haven't really searched for the info either) but according to one site I've visited a few times, the Bradley turret ring diameter is 150cm.
Does anyone have the the diameter for the LAV-25 so we can compare the two?
Information source
http://afvdb.50megs.com/
Specifically this page for the Bradley
http://afvdb.50megs.com/usa/m3bradley.html#M3