it should work. measure your current chainline (centerline of the seat post to the middle chainring), and check the specs on the new one...
http://techdocs.shimano.com/media/te...9830750016.pdf says a FC-6703 triple has a 45mm nominal chainline when used with the supplied BB. I believe shimano measures from the inner surface of the middle ring.
i note there are two different size adapters for that crank, 68 and 70mm, make sure you get the 68mm.