Thank you for the clarification.
Val Kilmer has an X post confirming it was said both ways in the movie.
The line was also delivered by Mariette Hartley in an episode of “Bonanza.”
Moon river, wider than a mile
I’m crossing you in style some day
Oh, dream maker, you heart breaker
Wherever you’re goin’, I’m goin’ your way
Two drifters, off to see the world
There’s such a lot of world to see
We’re after the same rainbow’s end, waitin’ ‘round the bend
My huckleberry friend, moon river, and me
Without question it is huckleberry.
The script also verifies it.
Here is Val Kilmer in 2014-I say both “I’m your huckleberry” AND “I’ll be your huckleberry...” I say it twice in the film.
https://x.com/valkilmer/status/534542290841112576
Historically it is huckleberry and has been used since the 1800s and in old TV shows of the 50s and 60s.
Once upon a time here on FR was a user with the screen name “I’m your huckleberry”… Absolutely fantastic posts