James Dean's final moments on screen

Is anyone as bothered as I am by the dubbing of Dean's final moments as Jett Rink?

In case you don't know, all Dean's scenes were shot before he died, and he'd done most of the audio dubbing as well except for his last drunken speech when Luz Jr spies on him from the doorway.

Re-watching the movie last night, I couldn't help cringe at how bad the actor's interpretation of Dean's voice was. It sounded nothing like him, was super hammy, and (IMO) marred what was otherwise a nearly flawless film.

I know it was necessary for them to replace Dean with another voice actor, I just really wish they had used someone who even slightly resembled Dean's voice.

Or maybe I'm just overreacting - did anyone NOT notice it wasn't Dean's real voice?

Just curious, thanks!