The math for converting the base malts is not complex. There are a couple of concepts to learn, including potential SG, PPG, and gravity points, which are also good to know when you brew all-grain. Understanding diastatic power is important to knowing what to mash, what it may need to mash with, and what to steep.
[Zymurgy’s 2016 Best Beers in America Results](http://Zymurgy’s 2016 Best Beers in America Results) (Zymurgy’s 2016 Best Beers in America Results) has some clone recipes - and provides both the all grain and extract versions.
Palmer's online edition of How To Brew (http://howtobrew.com/) probably has a section on recipe conversion as well.