In most cases, no special transformer redesign is required. TOR-5 is usually installed as an external system and connected to existing service points on the tank (typically oil valves/nozzles) for circulation and sampling, plus standard electrical connections for power and communications. What you may need is basic site preparation: suitable mounting space near the transformer, piping to the chosen oil ports, and sometimes adding a dedicated sampling/connection valve if the transformer doesn’t already have a convenient outlet/return point. But it’s generally a retrofit solution, not something that forces changes to the transformer’s internal design.