I don't think that the turbofan characteristics would have allowed the retention of STOL performance
-No blown area in the wake of the props (C-130J has stick shaker because it "can't" stall!)
-Less takeoff accelleration on a turbofan than on a Turboprop, no beta control available on landing.
things could work out if the turbofans were used in one of the powered lift schemes (USB, EBF, CCW...etc), but i don't see the point in installing turbofans, unless higher speeds are sought. if that's the case, you should redesign the fuselage and wing aerodynamics anyway.
Bottom line is, turboprops are a pretty uncomplicated way to get STOL if you don't need high speeds.
Turboprops are A LOT better than a turbojet, fuel consumption-wise. Of course it won't work for speeds above ~M0.62 (with very few exceptions).
Propulsive efficiency equations tell you that it's better, for a given thrust requirement T = massflow x speed, to take a large mass of air and accelerate it a little bit (Turboprop) than to take a small mass of air and accellerate it a lot (turbojet).
It's hard to compare directly a the specific fuel consumption of the two because one is given in pounds of fuel per pounds of thrust per hour and the other one is given in pounds of fuel per horsepower per hour.
You can assume that a turbojet has a bypass ratio zero and the turboprop an infinite bypass ratio. In between there are several possible configurations: Low-, medium-, high Bypass turbofan, propfan/unducted fan
The C-161J was a proposal for a civil variant, with main empasize, I think,
on easy loading/unloading of cargo and maybe on a higher cruising speed
and less fuel consumption. STOL performance probably wasn't that important.
"..turining any of the C-160's into a gunship platform like the AC-130?"
Nice idea, never heard of it and actually can't remember any such gunship,
that isn't of US origin (Is there any ?) ! So we have to create it on our own !
Fixed armament similar tom the AC-130 with a 20 to 25mm gatling and a 105mm
howitzer and, as air superiority is essential in any way, pylons for 4 GBUs under
the wing and the ability to self-designate using the targeting pod attached to the
right sponson. Then let's just add a FLIR turret under the nose, spherical observation
windows in the fuselage sides and in the ramp, which carries a launcher for flares, too,
and some additional measures for self defence (ECM pods at the wingtips and the fin and
chaff/flare launchers at the rear fuselage) and, voila, here's our Taliban Nightmare ! ;D
Sorry for that, I'm not really a What-Iffer, but it would be great fun for me to see this design
to appear again on certain sites, as happened before, for example to my Breguet "Forteresse