Welcome aboard Matias!
First step is read through the threads in this Engine Conversions section of the forum. There are multiple builds that show lots of photos about how to to modify the subframe to suit the 4EFTE. You should get heaps of info from those. I have a thread here as well on my build, but I tend to post with more photos and in depth details on my blog
http://mearcatmini.blogspot.com/ if you wish to look there.
Good luck!
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-Alan
I blame my dad for my love of minis. I think I was conceived in the back seat of one
I also blame my Dad for me being 6' 1" - not really the optimum height for driving a Mini.