Required usergroup selection at registration

[cicudaf]

Hi, my query is a little bit complicated and I couldn't find anything relevant anywhere on the forum.
I want to include a required field at registration, so users can select what usergroup they want to belong to. But I want to include only two options and not all the usergroups existent, like Administrators, Moderators, etc.
Take this example-
Are you a frog or dog?
Frog
Dog
After they select one of the groups FROG or DOG, the respective rank should appear in the postbit, user profile, etc.

My problem is... how can I put these groups at registration as a required field? Is there any mod or other solution? I don't want to create a new field with options that I have in User Profile Field at Options. I want a new field that allows users to select between two usergroups.

Any response will be appreciated! :D

Thanks.

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https://vborg.vbsupport.ru/showthread.php?t=267585&page=2 This is what I need, but it doesn't work for vBulletin 4.0.5. Any other ideas or mods available for this?

Thanks!