Downgrade to firmware 7.4.2?

Hi,

I'm trying to troubleshoot some network weirdness I'm seeing. Without getting into it, I thought I would try updating my firmware. I've done it several times over the years, but I can't seem to find my current version (7.4.2) available for download. In case there are problems, I am not willing to upgrade unless I know I can downgrade, as I have done in the past.

I found:

http://support.apple.com/kb/DL849

but clicking the Download button on that page doesn't download anything, but instead takes me to:

http://support.apple.com/kb/HT1218

which merely tells me about installing updates.

At the bottom, it has a link to:

http://support.apple.com/kb/HT1998

which merely takes me backl to the first link.

Can anyone please point me to the right location?

It is not on my computer where Apple says it should be, in a subdirectory of Application Support.

Thanks!