Here's (some of) the skinny...
"If they asked me, I’d certainly love to – let’s put it that way. But I don’t know what the script is. I don’t know what Arnold wants. I’m a big fan in fact of Conan. That’s a great movie and I found that the composer, Basil Poledouris, basically inspired many of my movies [the soundtracks] like Flesh and Blood, RoboCop, Starship Troopers and Total Recall. The score of Conan is great. The style of editing that Milius used was very beautiful, and Arnold does a great job. He was really the perfect choice."Source: The Arnold Fans