I'm having trouble finding a full installation of the latest version of 1.4, unfortunately. The MyBB team seems pretty adamant, understandably, to get people to install 1.6. Unless I've not looked hard enough, can anyone provide a link? And thank you for your offer. I will try it on my secondary server however and see how that works out.
You can download all MyBB versions from here:
http://wiki.mybb.com/index.php/Versions
Also, I forgot to add that after you update the templates and get the theme working in 1.6, you should export and install it on your forum, if that wasn't obvious already. You could do it right off your main website, but this is just to prevent any accident from happening.
Thanks. I'm experiencing a very annoying problem with configuring the new installation on my other server. For every page I go on in the ACP, it asks me to log in. I can't even import my themes because of this. Any idea what may be causing it? I had to create a new hostname but I've waited a few hours. The install was fine too.