So what are the differences between the 318 Magnum and the 360 Magnum? Is it just a different bottom end, or are the two motors completely different?

I'm asking this because I have a 318 and would love to eventually turn it into a 426 stroker...

 

The blocks are the same, same with the entire bottom end im pretty sure, I belive they have the same stroke with just a different bore.

Everythign is pretty much the same other than the different sizes.

 

the 318 is internally balanced and the 360 is externally balanced...and you also looking intoan 8 or so horsepower difference between the 318 and the 360

 

different main bearing sizes are the biggest difference in the bottom end other than the balancing. so no using cranks for 360 mains on a 318. best off finding a 360 block to start working with, all trans and mounting etc will be the same.

 

I'm pretty sure a 360 can only be stroked out as far as 408. Not sure about a 318.

 

So, if I wanted to do a build, I would have to get a 360 block?

Nope, it can be stroked to 426:

426-Stroker "HEMI-Sized"