Regarded as one of the best cabin class piston twins is the Cessna 340. It is about a mix between the Cessna 310 and Cessna 414, with a new fuselage. In appearance, it is quite similar to the Cessna 400 series. Like those aircraft it is a low wing, low horizontal stabiliser aircraft, with two engines in the wing leading edge. The single main landing gear retracts sidewards into the wings. The Cessna 340 has four oval cabin windows, of which the last two are smaller than the other two. Typical are the long D-shape cockpit side windows, which has a triangular inset on the left side, sometimes framed off. The aircraft also has tip tanks and a tall vertical stabiliser, with a long narrow dorsal fin and dito ventral fin.

The different versions of the Cessna 340 series can be recognised by 

• the shape of the engine nacelles
• the presence of vortex generators on the wings
• the number of ventral fins

These are all original Cessna models. It started with the Cessna 340. It has non-geared piston engines. The nacelles have (rounded) rectangular cooling intakes at the sides of the prop spinner. The 340A was an uprated version, with nearly the same engines. It is supposed to have three blade props with a 20 cm smaller diameter than the 340, but this would be difficult to distinguish anyway. The 340A came in two internally updated subversions, the 340A II and 340A III. Finally, the Cessna 335 is a non-pressurised version of the 340, but externally the same. The 340 and 340A can be modified with four blade propellers, and to one of the upgrades below.

To further improve the performance of the Cessna 340 & 340A, RAM Aircraft offers the Series IV, VI and VII upgrades. Most prominent are modifications to the engines, with the IV, VI and VII being different adjustments resulting in different performance. All have an additional cooling intake at the bottom of the nacelles. The standard intakes at the front are the same as the standard Cessna 340/340A. Additionally, they have a larger cooling intake at the bottom of the fuselage, in between the wings. Most modified aircraft also have vortex generators on top of the wings, near the leading edge.

Riley does similar stuff as RAM Aircraft, replacing the or modifying the standard Cessna 340's engines. One conversion is the Riley Rocket 340, which can be recognised by the location of the front cooling air intakes. They are towards the bottom of the nacelles instead of the top.

This is another 340 conversion by Riley. The Super 340, also known as R340 Super, has nearly the same engines as the standard version, but with narrower cooling intakes at the front. They do have a similar intake at the bottom of the fuselage as the RAM modified aircraft.

The Riley Super 340 has narrower cooling intakes at the front of the nacelles, next to the prop spinner. They are nearly a rounded square. (photo Ronnie Macdonald/WikiMedia)

This is another turboprop conversion, but with Rolls-Royce (Allison) 250 engines. The key features of this Silver Eagle 340 are nacelles with double exhaust at the bottom of the nacelles, near the front, and two ventral fins.