No. The 340 uses the tail and the landing gear of a 310 with the wings of a 414. The 340 has the air stair entrance making it a LOT easier to enter/exit than a 310. The 340A has the 310 HP engines. I did charter in a C-340A and normally carried 4 adults in back with luggage. No. Of all the pressurized planes I have flown, the only time I had problems was the few times when the out flow valve stuck closed so when the mains touched down there was a slightly noticeable ''pop'' in my ears as the pressure released. I never had a passenger notice it when that happened. A quick shot of spray lubricant and problem solved. (by approved maintenance, of course) A high altitude endorsement is required to fly airplanes that have a certified service ceiling above 25,000 MSL. I think the C-340 has a service ceiling of somewhere around 29,000 feet, so a high altitude endorsement would be required to be PIC on a C-340. Personally I never been over 18,000 msl in a C-340. Not a difficult endorsement, more time consuming than anything else. I did it while doing training for the C-425 in the simulator and added my IFR proficiency at the same time. Hope this answers your questions.