Custom font in Email content blocks

Has anyone figured out a way to use custom fonts in Marketing Cloud emails, where the font is specified only with Free Form content block level?

There is a hacky solution provided for full HTML emails in this question, but this method doesn't seem to work or I'm doing something wrong.

First encode font file on Base64Encode site.

Then create codesnippet with the code:

%%[SET @customFont = "T1RUTwAMAMKAAAMAQENGRiDCu2zDikEAAgTCuAAAwoITR1BPUzA.."]%%

Then add the @fontface to the block

@font-face {              font-family: CustomFont;              src: url(data:font/ttf;charset=utf-8,base64,%%=v(@customFont)=%%) format('truetype'); }

Then style the areas with simple

div {     font-family: CustomFont;}

However even just adding the @font-face to the Free Form will disappear after saving it.

Anyone else have had any luck using custom fonts with emails HTML?