Question on swapping panels in aircraft

Hi all, for example the Beaver, if the panel I'm using has throttle,prop,and mixture controls and I take it up get it on autopilot,straight and level, set up the Map and RPM for a certain airspeed and say come up 120 kts for the speed then swap the panel for another single engine panel with throttle,prop, and mixture and set up the same flight with the same setting will or should the airspeed be the same?if yes okay, if not then why not!!http://www.enter.net/photoalbum/data/reddog/596406.jpgUSMC Retired