Looking to replace my 273 with a 318, which one?

Hi buds, thanks to your help you've steered me almost completely in the direction of a 360. I was thinking of this 360 crate from Classic Industries which you can look at here http://www.classicindustries.com/mopar/parts/mn2472.html

Now I know I need an LA engine, and this says it's a retrofitted magnum engine meant to replace an LA engine. What do you guys think? Thanks in advance for the help & suggestions. Please bare with me if my Mopar questions sound stupid, I am a Chevy guy after all and need y'alls help. :D