Say Again:
Slightly off-topic, but I did once fly the Basler C337 conversion which is on your same principle...remove the aft engine, convert space to a clam-shell cargo/ambulance/whatever space, insert a 3-foot plug in the fuselage for another row of seats, slam a PT6 in the front, add bigger tanks.
Result: less levers, greater payload, longer range, more comfort, etc, etc...and most importantly...less NOISE!
(forgot the $MM bill, though, but came with leather, new avionics, paint etc). (They do the same for DC3's, you know).
{edit to apologize to Mr Proachpoint for going off-topic}