Sorry I missed this question.
Yes, the digital engine gets completely changed out to the new engine 53. The analog stage is mostly changed as well, including the tube heater circuit. There are server parts substitutions throughout--it's a significant rebuild.
It is available for regular Atlantics as well as Golden Atlantics. The Golden variants are the same fundamental circuit with superior components throughout (caps, chokes, resistors, footers, chassis, grounding, etc.) and few other changes.
We also offer affordable rebuilds of Atlantic series DACs to Atlantic 2: TRP.