Figuring a T25 size turbo, 8psi is doable, 10 if you are conservative about it. Tuning is a must. Boost is addictive, the first day you'll run 6 psi, the next day you'll want a little more, then a little more, until you are running 12psi and the engine blows up.

Rods and pistons would be nice, but it helps to know the intended boost and the turbo you want to use, i.e. 6psi out of a T25 is a bit different then 6psi out of a T3/T4.