I'd also suggest rebuild, then you know it's all happy days, who knows what the second hand set would be, difference between 3.55 and 3.73 is only 5%.
I rebuilt mine, regeared, fitted Aussie locker etc, local machine shop helped with advice and press fitting where needed, hit the jackpot as they had a Wrangler that needed a rear diff carrier, so swapped that for all their help, happy days.
Plenty of info on nerdy net, this site, very rewarding job, good luck, Maf