400 on a 300

[duke416ex]

How hard is it to put 400ex plastic on a 300ex? What will I have to change and what will I have to buy extra. i am redoing a 300 for a buddy and trying to save some $$ over the 300 plastic and helpit look good too.

[YZ400EX]

I am in the process right now, so after I am done I can posts pics..