I'd be hard pressed to pay $1000 for a re-bored '86, but they are climbing in price at a steady rate. It's a shame that the owner didn't have the barrel lined to the original caliber, 'cause the .40-82 is a fine cartridge that is capable of taking most North American game, large or small.
The crescent butt was standard on the 1886; anything other was a special order item. Standard barrel length was 26", with most being octagonal. Octagonal barreled Winchesters seem to fetch the higher prices, but round ones are actually scarcer.
The rear sight issue is another negative, however, many sights were replaced by what the owner perceived as better. A gun that has been altered is not a collector gun anyway, it is a shooter and hunter rifle at best.
I would rather spend the money on a new '86, one that can withstand the pressures generated by modern reloaded .45-70 ammunition.