Lets think about this
The Cessna 340 is a great plane. With RamVI’s and VG’s the published rotation speed is 91 kts with a climb out of 108 kts to safe altitude. To consider speeds below these is crazy. If an engine pukes on takeoff, forget the catlike reflexes and honed skills, get real. If you don’t value your life maybe you wife, child or passenger does. That 335 horse engine hanging on the right side is producing significant torque and is purpose built to roll you over if you are not prepared. It takes time, maybe four or five seconds to stop the fuel flow and actually stop producing power, not to mention the inertia that 2700 rpm of all that machinery spinning takes to slow down. It takes probably 2 rpm, or .000741 seconds with a busted crank to stop the inop engine. That 335 horsepower on the right wing can lift one hell of a lot of metal in 5 seconds without proper counter forces in an asymmetric engine out scenario.
Regarding runway length, I will not fly mine into anything less that 4,000 ft. Landing in 2,500 ft is no problem; however the engine out on takeoff scenario requires a few more considerations. To accelerate to rotation speed, liftoff, have an engine fail and land safely requires at least 2,700 feet for Sky King to do. So why push it, include a safety margin.
If the mission profile does not fit the 340, look at the Maule or the Caravan or other purpose designed short field aircraft. Don’t buy the 340 because you can get a great deal on one and make believe its got STOL capabilities.