There may have been all of one SU-76i that was recaptured and put back into service by the Germans. As to whether it was ever dressed with Winterketten... we need some good data and evidence on that.
There is at least one picture around showing an SU-76i with the Pz. III cupola mounted (and with the altered casement-side to allow this installation). Paul Owen has posted that picture on Track-Link.com.
I personally think that Paul's picture is of one of these SU-76i built as a unit-command version by the Russians - and that the cupola was added by them for that use, and not some post-recapture modification by any German shop. But that's all just my opinion!
The picture Paul posted is quite interesting, as it suggests that the conversion was done on a captured III-F or III-G tank - it has the hull escape hatches, a mid or later-version idler (I think...), the later wider road wheels for the 40cm tracks, but a widened early-version sprocket of the sort fitted to F and G to use the 40cm tracks.
Sadly, it looks like Dragon intends to tell us that their kit represents a recaptured vehicle which has reputedly been re-fitted by the Germans with a cupola and winterketten. And the Dragon kit evidently will have the later version sprocket. BAH!
With the added cupola and a widened early sprocket, and early version 40cm tracks, one could build a legit model of one of the known Russian command SU-76i. Can one build the possibly only one recaptured SU76i from this kit? I have no idea!
Cheers!
Bob