A W7-8-9 uses a dry intake.. meaning it doesnt
have water in it.. W2 and W5 are wet intakes
that have water in a couple of ports.. I have
never tried to put a W7-8-9 on a w2-5.. can it
be done.. yes with some work
EDIT
Also the W-7-8-9 use a valley pan and the W2-5
dont..they have a built in valley pan