Center chunk

Ring and pinion need to stay with the proper case (489, 741, or 742) but sure, you can have a 489 for the track and put a 741 or 742 back in it for cruising, no problem. And as was said earlier, you can swap a suregrip from 1 case to another, just keep the carrier bearings with the suregrip. (bearings and races are different between them but the OD on the race is all the same)