front a-arms the same 5.0 to 4cyl?

my balljoints are bad, my friends ordering me the stuff for them, we were going to go to a junkyard and get some front a arms off a 4cyl (all thats there) and put the new joints and bushings on that, so we could just switch the a arms out, but i dont know if they are the same? are they? police/taxi ones are too expensive for me..

side note : foxes come with trac-loc limited slip right?