I don't know all that Clément knows about what DF v50.?? versions (or indeed prior) work or do not work with DT, but surely (prior to this, with your 47.05), Legacy and SDL versions were effectively the same w.r.t. (vanilla) graphics of the Codepage type, though it does muddle the back-end/internals around to require a technical change to DT connectivity..
Check
http://bay12games.com/dwarves/older_versions.html and get the appropriate SDL download (64-bit, if you wish, if you were running that assemblage already) for 47.05. I don't think the Small version changes anything of consequence to you, if you prefer that for whatever reason. Unpack it parallel to your Legacy version (should be easy enough to do, even if you used something like LNP to manage this deployment last time) and copy across the Savegame folder from the "legacy" version into the new one and then... I
imagine ...you surely won't need to either start a new fort or lose out on DT functionality. Unless I'm totally wrong.
Maybe you also need pre-Steam version of DT (not something I've yet had cause to test), though I'd have to read back through the thread updates to see if there were various clean-breaks made for the sake of Clém's surviving sanity. Perhaps I missed/misread something about this that meant it had been breaked cleaner/harder..?
And I'm so behind the curve that I couldn't say if v50.xx unPremium is "new Legacy" ('deSDLed'), or not, but I've not been given that impression (and it's irrelevent to the 47.xx era anyway), as "non-graphics"/”ASCII" DF was
supposed to be just "Steam-graphics DF" without the fancier Premium resources, SFAIK. Not that it matters here.