What to look for in a 351W?

I found this listing for a 351W, I probably can't get it now, But I plan on droping one in my 69 at some point. What sould I look for/avoid and how much time/money would it be to do a basic re-build on one like this? Thanks.

Here's the link: http://sandiego.craigslist.org/pts/176481040.html