Ubuntu :: Hardy Downgrade From Firefox 3.6 To 3.0?

Short version: I'm running Ubuntu 8.04 (Hardy Heron) and need downgrade ASAP from Firefox 3.6 back down to Firefox 3.0. In Synaptic, the firefox-3.0 package cleverly now shows up as version 3.6. How can I downgrade? I'm open to anything. Long version:

I just did a security update on my Ubuntu 8.04 (Hardy Heron) installation. It upgraded Firefox from 3.0.x (x=19, I think) to 3.6.x. This broke an absolutely critical plugin for me, pretty much the one and only plugin I care about, and one that doesn't support Firefox beyond 3.0. More on the plugin below if you care.

But for now I MUST downgrade immediately to Firefox 3.0.x. I realize that The Powers That Be probably forced us to upgrade to 3.6 for a reason (i.e. 3.0 isn't supported anymore, or something like that) but I really can't deal with a 3.0-3.6 sea change right now. I need to get the FF install back down to 3.0 pronto. My work is piling up fast.

If there's no way to do it within the carefully security-controlled world of officially-supported 8.04 LTS, I'm open to steps that will force it. I just need my FF 3.0 to work for a couple more months.

Related question: If I downgrade, what are the chances that FF 3.0 will be able to parse my (carefully crafted) profile, now that the newer 3.6 has gone in there and presumably mucked it up with 3.6-specific things? I can extract the 3.0 profile file(s) from a backup if needed (a snapshot was taken just before the security upgrade!) I'm not going to say what the plugin is, but it's critical to me. I literally can do virtually nothing without it. I will find a replacement for it (one that supports 3.6+) when I tackle the OS upgrade, but NOT NOW

Sidebar 2: I know 8.04 is a little old, but I don't have the time right now to deal with upgrading. It's a massive undertaking for me to do that, and I plan on doing it in the fall (read: not now!) As part of that OS upgrade (wipe and reinstall, actually), THAT is when I would tackle migrating to a newer version of Firefox, including figuring out all the preference adjustments to get it to my liking and, most importantly, get my critical plugin to work. And that's also when I would upgrade to FF 3.6 (or whatever) on ALL of my machines. I have several computers (Linux and Windows), and I keep them all at the same identical level of Firefox, with the same prefs, and that same critical plugin, so I have the same browsing experience and feature set no matter which computer I'm at.

Sidebar 3: While I'd love to sanctimoniously wag my finger at Ubuntu for doing this Terrible Thing to us users, I imagine there were good reasons for it and perhaps was even some debate about forcing a 3.0 -> 3.6 update. I'd love to see that debate, if someone can point me to it (e.g. a bug discussion thread on launchpad).