You should have used Final Cut Pro > Easy Setup prior to capturing/transcoding footage. That is the bullet proof way of dealing with different formats.
Just re-import the footage with the proper setting.
Please, since you are new, post questions like this in the FCP Basics forum. No offense, but we try to keep the basic questions over there to keep the noise down in this forum. The advice there is just as good as this forum, it's just for more basic questions.
Thanks.
Kevin Monahan
www.fcpworld.com
Author - Motion Graphics and Effects in Final Cut Pro