I do NOT take any credit for this. All credit should go to Mozilla for bringing Firefox to armv6 devices.
I know this is pretty old news. But I'm doing this for people who don't know how to.
Here's the link to download Firefox onto your LG Optimus V: Firefox Alpha armv6.apk - File Shared from Box - Free Online File Storage
If that download didn't work try this:
Firefox Alpha armv6.apk
You don't need to be rooted to install it.
Instructions for noobs:
1. Download the apk file onto your phone through the browser.
2. Go to your settings then applications and check unknown sources.
3. Find the apk file with a file browser like Astro File Manager.
Link for Astro File Manager: https://play.google.com/store/apps/details?id=com.metago.astro&hl=en
4. Open your file manager and go to the downloads folder.
5. Click on Firefox Alpha armv6.apk
6. Install and enjoy!
If it opens like a HTML Viewer, try this:
1. 'Long press' on the file
2. Choose Rename
3. Erase everything and type ' Firefox Alpha.apk'
Make sure you have the '.apk' at the end!