Making a MP3 a Podcast

I have some MP3 files that I want to make show in iTunes under "Podcast".

From digging around I learned that Mp3tag would set an extended tag "ITUNESPODCAST" to the value of 1 and this would fix my files. But when I do that they still do not show up as a "Podcast".

If I take an actual podcast, save it to a directory & look at the extended attributes with Mp3tag and set my file to have the EXACT attributes it still doesn't show as a "Podcast".

Please can anyone give me some advice on this?

This tag can only influence the display in Library > Music but not in Library > Podcasts

I think you can only get Podcasts to Library > Podcasts by subscribing to them in itunes.

There are actually 4 tags that you need to adjust:

I believe that they use the last 2 to determine which podcast group to file
the program under. You need to be subscribed to the URL in the last for
this to show up in the proper place.

Also, if you use RELEASETIME, you can add the podcasts sorted.

But I have a problem related to this:
I read about how to do this, and have tried the method for mp3-files, and it works well.
Where I found this method it said it would work for any file, but I have problems with video.

When I open them in mp3tag, they don't contain any tags at all.
I beleave that I could just add them, and it would work, but I need the correct ITUNESPODCASTURL from one podcast already correct in iTunes, because I want them to appear in the same place. I could always guess, but I figured I post it here instead...

The files I have tried are mp4 m4v and mov
Any thought?