I would just change the viscous coupler and put a stock drive shaft back in. With a good viscous coupler (only the 96-98 style is available now I think), there really is no advantage to swapping to a 231 (other than having 2WD for burnouts). The 242 is a horrible transfer case. The Full Time option is really pointless since there is an open differential in it. So all it takes is one wheel to lose traction and you're going nowhere. You then have to shift into Part Time to get moving again. Tell me the point of Full Time now? Plus the 242 is EXTREMELY picky about linkage adjustment. Plus they get stuck in one position requiring rolling back and forth to get them into another selection.
The 249 is stronger, and with a new VC will outlast the Jeep at this point (honestly, do you REALLY think your Jeep is going to last ANOTHER 150,000 miles?).
No modifications to the Jeep required, no getting a shaft shortened, etc.
But that's just my opinion. Take it for what it cost you.
1997 ZJ 5.2 Orvis, Baby!
1953 Willys M100 trailer Tagalong