use any file explorer with root permissions and or adb. Assuming a file explorer copy the old apk to the system app folder and paste, overwrite. Then either change the permisions on the app to match that of the other apps in your system folder, should be
I doubt the ICS browser will work on HC but I will give it a whirl when I get my flyer in hand. When I was running ICS though I did not notice any major differences between ICS and HC browsers. If it installs and runs I will post the APK