the front blade for the 96 sight is shorter than the blade for the 1898 sight so theres a solution for elevation. All joking aside, maybe at 100 yards or 200 yards the elevation would be right on anyway. Shoot at 100 yards?
I take it this rifle is so beautiful you don't want anything but an 1896 rear sight on it? As already stated a 1901 or 1902 rear sight will solve all your problems and would be perfectly legit and cause no harm to the rifle.
Meantime 1896 rear sights, if you want to alter one, are on ebay every day.
Post photos and it will be fun to see how you solve this.
"A man with a tractor and a chain saw has no excuses, nor does he need any"
Me. "Consistency is the hobgoblin of little minds" Emerson "Consistency is the darling of those that stack wood or cast bullets" Me.