As DI757MD stated, #2 engine is hanging from a pylon attached to the rear spar of the vertical stabilizer. The whole structure is a bit complicated to explain, but basically you have 4 socalled banjo fittings, huge titanium forgings, looking like a ring with an attachment on top and on the bottom. The bottom attachment is connected to the rear fuselage, while the top attachments connect to the four spars of the vertical stabilizer.
The hole inside the rings is the inlet tunnel of #2 engine.
The fan case of #2 engine is bolted to a unit called a bell mouth, wich has a sliding connection with the inlet tunnel (so that the engine can vibrate and move without disturbing the structure of the inlet).
The engine mounts and accessories of #2 engine are slightly different from the other two engines. Additional to the two mount plates on top, which transmit the engine weight and thrust to the airframe, there is another diagonal brace at the bottom connecting the engine fan case with the lower attachment of the last banjo fitting to carry the torque forces of the engine and to transmit them to the airframe. Also, on the CF-6 engine, the hydraulic pump supply line comes from the bottom instead of from the top.
#2 engine also has a remote manual start valve mechanism with a push pull cable leading to a handle in the tail cone compartment. Additionally, there are remote service lines for both the engine oil tank and the IDG plus a remote IDG filter differential popout indicator, also located in the tail cone. You can´t just install a wing engine in the #2 position, you´ll have to modify it slightly before.
The reason for the DC-10 / MD
-11 #2 engine layout was that they wanted to have a straight inlet to give the engine full performance, unlike the 727 or the L1011, where the s-duct restricts the performance of #2 engine.