How much boost can I run on my car and what turbo would be the best choice?

I have a 1996 ford escort 1.6 16v Zetec 4x4 that I want to turbo convert. I'm planning on running it with stock internals. What would be a safe boost figure and what kind of turbo would you recommend for it? I will be using it for the streets and not the track.

I suggest you read this:
http://www.fiestaturbo.com/tech/zetec-turbo/
The limit with out a lot of work are the injectors! http://www.witchhunter.com/injectorcalc1.php
Boost determines hp and is proportional in atmospherics'! 7.5 lbs would produce a theoretical 50% hp gain.
Many feel that 7 lbs boost is as far as the stock injects can carry.

I wouldnt go above 9 psi. If you go to a junk yard and find a turbo charger off of a powerstroke diesel you can usually pick those up for like 2-300$ and then build the rest of the kit yourself for pretty cheap.