Ok, so why are you looking at list prices for ready made kits then? I bet you could twin turbo a 5.0 for less than a grand. Matter of fact, I bet you could do it for less than 500 if you already had a suitable fuel system and such.
Back before I was going to drop in a TC motor in my LX and bought my SVO I was researching turbo kits for my LX. I ran across a few links but they was all for 5.0Ls. If you can Turbo a 5.0L and even twin turbo it for 1k or less than hell ya I would go for it
My view has always been this : (sorry if it sounds harsh, I am a bit drugged from some dental work right now)
If you have to ask if it can be done, and how much you can do it for, you probably had best not do it.
One BIG benefit of a turbo over a belt driven charger is crank/bearing wear.
When you start running high boost from a blower car you need a tight belt to keep it from slipping. This can put an ENORMOUS load on the front bearings/crank snout to cause damage.
Having pulled apart several higher powered blower cars, the increaed wear is phenominal in some aplications.