There was a different ending? Saw it in the theater with my dad but I was eleven years old....have the newer release now.
The original ending had Capt. Willard answering the Box Car call with his code ( I can’t remember what it was, and it called in B-52 strike, obliterating Kurtz’s whole camp.
I think Coppola changed the ending after the first run in theaters.
He was mocked in a SNL skit for not being able to make up his mind.
The strike put a decent end on the movie, ( and made up for what happened to Frenchy ;) ).