If you remove your head to change the head gasket to a thinner one, you will most likely need to get the head lightly machined to insure that it's entirely flat. If you want to raise the comp, it should only cost an extra $50-$60 on top of the initial 'clean up' machining, so you could probably use a standard gasket again.
The 3.9 has a compression ratio of 8.8:1, apparently, if you raise the comp past the 9.2:1 point, you actually begin to loose power.
Head porting is always good to a certain extent. The inlet ports of the 3.9 are pretty good, and only need minimal work. The outlet ports are pretty ordinary, and require a little extra attention. Remember that bigger ports are not always better, and that porting helps out at higher rpm, and sometimes sacrifices lower range power to do so.
Crow Cams is the was to go if you want a little extra balls www.crowcams.com.au
Turbo kit for an EA for $1000-$1500 if ya know someone who can wield.... more details PLEASE!!!!
I have a mate that owns a metal fabrications factory, and another that wielded an entire drag car together (profesh wielder) and another that wields extractors for a living.
I WOULD LOVE TURBOOOOOO!!!!!!!!!!!!! :p