Changing an installed system from i386 to amd64

[Pete French]

I have a box currently running i386 which I want to change over to
run amd64. I have installed a second drive into the machine on which
I have put a basic install of amd64, and have compiled up the world
and kertnel from source.

Can I simply switch the original partition over by mounting it up
and doin a 'make installworld' with an approrpiate DESTDIR set ?
I guess what I am asking is if anything else is different between
the two versions aside from the actual binaries themselves (i.e.
directory layout and the like).

-pete.