Test Group Conversion Tracking / Testing

Is there a way to setup and define a conversion within Marketo to be a link click?

No, but you can have a form that only contains a link as its submit button. Therefore the link click will indeed be a Fills Out Form activity. However, a caveat is that if the lead does not have an associated session (you haven't said whether you expect anonymous traffic to the page/s) then you'll be creating a lead when they click, though the lead will not have an email address. Thus you'll have to manage future form submissions carefully to merge their old and new web activities.

Also, please use a real name as advised in the Community guidelines, if possible.