this is very hard to do!! i found that by putting the stem(body)on top of some blocks of wood so that the quill goes through the bottom of the vice jaws,then heating the body up with a blow torch near to stem bolt works,you need to leave the big bolt in but undo it slightly then whack it with a big hammer-this is the easy bit because any marks can be sanded and polished before re-annodising,the trick is then how to get the quill back in the body without damaging it
i tried putting the body on some soft wood then hitting the bottom of the quill and tried putting it in the vice but found it went in at a angle which you don't want as it takes off some more aluminium then not making it a tight fir any more
i gave up in the end