[ab01]

The center engine inlet may have been somewhat oval. You can tell from the engine mounting strut that it is most likely a side-mounted engine. It is not a 747, 737, nor DC-10

[leadpenny]

I agree it could be a 727 (not 100), but the mounts suggests it is the center engine. The mounts on side engines in pic above are too close to the fuselage.