P-51 Mustang (Tamiya 1/32) Merlin V12 Engine Replacement Diorama

   Kiwi mentioned the crane hieght earlier in this thread.

I am thinking a plane being worked on that extensively would not have ammo in the gun bays.

The Merlins and the Allisons had at best a 300 - 400 hr. Life before a switch was required. Remember, they were being used up fast in the aftermath pf Dogfights!

 They were lucky. Any edition of either engine had a life expectancy of 200 hours  in any Patrol Craft or Torpedo boat involved in heavy attack work!

 The ones in Hydorfoils were cut to 100 hours at best! As far as Ammo in the gun bays, maybe he was about to do a mission and the engine gave up the ghost!

Typically, engine removals/installations were accomplished by jacking up the rear of the plane so that the engine to be pulled sat parallel to the ground and, consequently, was ready for the new engine to be installed. This was also done when setting aim points for the guns. A good example of this {shown very briefly} is the scene from Pearl Harbor {the one with Ben Affleck} where the pilots and crew are test firing and setting aim points.