successful LSX swaps into porsches have been going on for awhile. the 911, and 928 and that whole line have many MANY examples even the 914.
now the boxster is something a little bit special in the fact no one has done this before. but currently a guy named Brad Roberts is in the process of developing it. according to him he has everything all set he just needs to get it started and rolling.
Now, his process has been a little bit slow because he is trying to develop the kit and not just make this a one-off. according to him he will have a running kit v8 boxster hopefully by the end of the summer.
there are a few threads floating around about this topic but due to some issues he has had with other people on the forums he doesnt like to come on much, and he has shut down his own boxster site.
here is the closed site that has information in contacting him
here is the 986forum thread on the v8 topic.
hope this helps you cause of frankenporsche
