What temperature(s) should sweetbreads be cooked to?
While not perhaps a definitive answer, according to Serious Eats:


  Besides its amazing flavor and texture, sweetbread is nearly impossible to overcook. [...] you can sear the exterior of sweetbread to your heart's content, without worrying about the interior turning chewy and tough. Your cooking timeframe, in other words, is extremely forgiving and long—minutes long, rather than tens of seconds.


This implies that sous-vide is perhaps not as helpful for sweetbreads as it might be for some other foods that are more temperature sensitive.

The only recipe I could find that mentioned a temperature was a sous-vide based recipe that suggested 60 C (140 F) for one hour.  Note that this is one of the time and temperature combinations that essentially kills all pathogens that may be present.

From these facts, I infer that you want them cooked though (which the traditional blanching method will ensure), and hot for service, but a specific temperature as is used for beef is not important.