actually...thats not true at all. A properly sized turbo would actually net you much more horsepower than a supercharger...however, its all in what you want.
A supercharger will give you low end mid range power. Meaning, as soon as you hit the pedal, your already making boost, so...it just keeps pulling till you shift. However, it loses efficiency at higher RPM (at low end, if it makes you 150hp, it takes 20hp - at high end, if it makes you 150 hp, its taking 75hp to run it). A supercharger takes power away just to spin it, meaning that you aren't getting the full gain from it. But, its still definitley worth it, and...if your just looking for some street fun...would probably be the better choice.
Now...a turbo takes absolutley no power to run it (it uses wasted exhaust energy to make boost). However...its drawback is that it is more geared for higher RPM power. You won't see full boost until about 3000RPM. Also, it is much easier to intercool a turbo, resulting in even more power due to the cooler air charge. Where a turbo would be better is on the track all out drag racing...or even something as simple as pulling a heavy trailer.
Also...superchargers put more stress on an engine then a turbo does. Because, a turbo is only making boost when you put a heavy load on the engine. A supercharger, however, is making a set amount of boost at certain RPM no matter how you drive it.
So...as I said. Its all in what you want out of your truck.
A supercharger is easier, being more of a bolt on affair...whereas a turbo will require installing new parts, and/or fabricating new ones, running vacuum/boost lines, plumbing the wastegate/intercooler piping.
Both will require some computer modifications (ie, more fuel to support the increased amount of air).
I would definitley install a cam to maximize the power increase (with a turbo engine, you want more valve overlap, however, in a supercharged engine, you want very little).
Also, with a turbo you will need a very free flowing exhaust as you want absolutley no backpressure behind it, which will help spool time a lot. With a supercharger, you want free flowing exhaust, but, as with an N/A engine...you don't want it to flow too freely, as you want some back pressure.
Also, I would recommend a wideband o2 sensor with a gauge with either route to monitor your air/fuel ratio so you can see a problem before it causes a bigger one.
But, figure out how you want your truck to perform (low end/mid range, or top end) and what you will be using it for. This is the most important factor in your decision.
Supercharger = low end/mid range (red light to red light)
Turbo = mid range/high end (all out drag racing, pulling a trailer, driving in a very hilly area)[on a hill, you can leave your foot in the same spot...the turbo will spool up, making more power, and the engine can pull you up the hill...all without even moving the throttle. Pretty cool actually)
As far as your trans...I'd put a shift kit in it, and maybe even upgrade the torque converter. But, as long as you aren't going to crazy power levels, I would think you'd be okay.
Either way you go, though....you'd have to keep boost relatively low. I don't know what your static compression ratio is...but...its higher than most boosted engines. So, something to keep in mind.
If you're really planning on going all out race truck...as set of lower compression pistons would be a good upgrade, so you can up the boost safely.