the 231 has a slip yolk on the rear drive shaft (unless it has a sye kit installed). How do you know it is the transfer? Has it been making a racket? Around here a 231 will cost you about 250.00 at the junk yard (if you can find one). There is also a 242 transfer that will bolt to your trans, but I think the yolks are different(the spline count or something). As for "is there a better one?",....the 231 is about as good as there is (stock) without going to some aftermarket,high dollar deal.
I would try to check everything out to make sure it is the transfer before I bought one.