converting FLAC to MP3 with "all" the tags, currently looking for TDRL and UFID Options

[HansBKK]

I'm mostly using Picard and MP3Tag for my tagging needs, then using FB2K to handle the FLAC to MP3 conversion.

(apologies if such a question should be in FLAC, I'm guessing here)

I want to automate the conversion of my VorbisComment tag RELEASETIME to ID3's TDRL, and MUSICBRAINZ_TRACKID to ID3's UFID:http://musicbrainz.org.

If this isn't possible with FB2K, then I guess I'm looking for a different free tool (in either/both senses) for handling such conversion, carrying over as many as possible of the tags over - coverart, maybe even lyrics would be nice but not that important at this point.

I'm noticing that I have to change quite a few of MP3Tag's default mappings in order to get the ID3 tags converted properly (e.g. CONTENT GROUP rather than CONTENTGROUP, COMPILATION, TORY, all the SORT ones. . .)

And ideally not just the one-time tag transfer when encoding, but even updating the ID3 tags when the source FLAC fields are edited later on, but I realize that's most likely a bit of a pipe dream.