I don't know a mod to do this off-hand, there may be I just never cared to look...
But you could do this on your own by making a custom profile field "User Profile Fields" on the admin cp menu... Make a drop down box, add all your pre-defined titles... then add the field to display in your postbit manually.. just drop in the code:
Code:
<div>
$vbulletin->userinfo['field7']
</div>
replace 'field7' with whatever name you get from vbulletin when you make your new field. There is an article you can search for for more help in adding custom fields to the postbit. (or postbit_legacy, whichever you use).