grant tables update backward compatibility

[zeus]

Hi there,

I have been using mysql 3.23.58, and I want to upgrade to 4.0.20.  My question is this:
after I run the script to upgrade the grant tables to support the new privilgeges, can I
then revert back to 3.23.58 seamlessly or will I need to readjust the grant tables. 
Thanks in advance.

-Bob