The Whirlwind "Winch Pack" was a self-contained hydraulic winch assy that could be fitted or removed in a short time - perhaps 2 hrs with functional checks.
Obviously several mods were required to install a new hyd pump, some pipes and wiring and structural changes.
The pack was mounted in the same place as the standard winch but connected to two (Avery) Hyd couplings and two electrical sockets (one for the Squib) above the cabin door and in front of the top platform/step
There were no internal wire runs or pulleys and no winch in the baggage compartment in the back.
I never worked on the standard packs - Training Command didn't have them!