I'm confused and I need advice. Can anybody help?

I dated this guy for a couple of years, it wasn't all easy for us, as you can imagine, but he was a nice guy. After we broke up, we didn't speak for a while. A couple of weeks ago, we started talking again. I'm fully and completely over him. However, he said that now that we're talking again, he likes me again. He's a nice guy, but I have no feelings for him whatsoever. In fact, I like his best friend. He knows I liek his friend, and we talk about it quite a bit, and he makes me feel better when I get upset that his friend doesnt like me. He actually told me that his friend did like me, and he thinks we would make a good couple. My problem is, I have no feelings for my ex, but I don't want to wreck our friendship again. So how should I go about conserving my friendship AND getting his best friend?