Daryl,
For your turbo setup, IMHO, there is no better cam than the factory cam.
Also, if you have designed a decent turbo system, you will be able to
have the same engine life as normal.  Referencing the turbocharging
book "Maximum Boost", by Corky Bell, Porsche engineers have said that
one racing mile is worth about 1000 road miles (their cars have run
thousands of racing miles without blowing up).  Therefore, with the
proper preparation etc (doesn't have to be thousands of dollars) you
can have factory reliability.

Referencing the book again, "no lag = no power".  Also, you are
reducing engine longevity by running a too small turbo because the
smaller the turbo, quicker it spools up, the larger the backpressure
on the system increasing exhaust heat and wear on parts up the line
and in the turbo.  So, bigger is better (upto a point).

In my experience with turbocharging the flat-4 (one car that we blew
the engine up on because we wanted to see how much boost we could run
with stock internals).  Go with twin smaller turbos, one for each
cylinder bank.  While this does not guarantee more power, you will run
cooler since there is less backpressure.

Anyways, I am going to be designing a turbo system once the stock
engine goes back in the van.  I'm sick of blowing transmissions with
the 200lbft torque of this chevy motor, so please keep me up to date
with your experiment. :)

~Sudhir