At 120K, your engine is in no shape to add a blower
regardles how good it seems to be now.  I have installed a
couple of blowers on the 5.0 in trucks.  The only way to do
the job for the average Joe with no advanced automotive
engineering skills should look for a complete kit that
includes each and every fuel, emissions & fuel control
componet that is selected to work together.  As far as
reliability, you can count on going exclusively to premium
fuel with a blower.  The increased output resulting from a
blower or turbo will result in doubling the load on various
engine components resulting in shorter life and reduced
reliability.  If you still use your 5.0 truck as a truck,
you will need upgrades on your cooling system including oil
and water as well as the transmission.  I assume you have an
automatic.  The manual in the F150 doesn't stand much of a
chance behind a blower.  An automatic can be modified and
beefed to somewhat handle the job.  Again, if you tow much
weight, the trans reliablilty will be greatly reduced.  You
wil also need a complete exhaust system from the engine back
to let the engine breath once you do this.  Your area may
require a cat converter.  You may never be able to get it to
pass emissions if your area requires testing.  Any way you
go at this, you must realize it is an expensive proposition.
You may want to consider a much newer truck to do this on as
a complete blower kit with mods done right is going to set
you back over $5kUS - More if you build the engine into
proper mechanical condition to handle the job.

You are going to hear many of the good things about a blwer
or turbo which are probably true.  You should understand
this project is not for the mechanically marginal nor weak
of financial resources.  My brother is stil wrenching on a
Bronco he decided to blow a few years ago.  Since he has
refused to give it up, he has invested well over $50k in the
powertrain in less than 50k miles.  Right now, it is
sidelined awaiting another mod to help reliability.  He has
finally gone to a stock 351 powered Bronco for a daily
driver which he finds much more enjoyable to drive than the
blown 5.0 Bronco.  He also now has the ability to tow his
four wheelers on a trailer w/o fear of destroying the trans
or melting a piston.  It is much easier to abuse the engine
and trans without even knowing it with a blower.