Mike wrote:

Well, It appears that I'm not the only one confused about core types.
I do have some FT50-43 cores, so I think I'll try that first and see
what happens.

Thanks to all for the suggestions.

Those are type 43 ferrite (Fair-Rite designation), the most common kind.
Your cores will be just fine for this and similar applications.

You're definitely not the only one confused about core types. Very few
people seem to understand what the requirements are for cores used in
various applications and therefore what cores are suitable for a given
application.

Roy Lewallen, W7EL