Throttle
You beat me to it. Conquest 11 a legend in its own time.
I think I still hold the record for Perth-Coolangatta FL 330-350 (avge wind +35) non stop at 6+10 arriving over Cooly with fuel for Sydney with reserves intact. B200 can't get even moderately close to that.
I have even been westbound Syd Per non stop many times going easy.
In practical terms there is no such thing as long range v high speed cruise, 290 KTAS any way you wanna do it.
Only problem was I had too many cups of coffee the toot was too far down the back and I ran out of coffee jars.
nasa
They already built the aircraft you describe and its called a Conquest 11. They really did try the PT6s on it, but could not get any where near the performance or payload range they were looking for and in any event the Garrett is a much much better more efficient engine. Why you would want to torture the air by making it go around no less than 3 x 180s before you let it out to play escapes me just for the moment.
King Air B200 = Dinosaur
C-90 = only just post Big Bang.
