Just wondering if it will make much more power
To gasket match the heads and intake.
Is there any dangers involved in terms of messing up the sealing surfaces ?
I guess a die grinder with a carbon steer bit would do it.
Typically, gasket matching will not help torque/power production and in many cases will hurt it. The gasket is relatively large compared to the port size, and you don't want to open a small section of the port to a nice big size, while the rest is narrow. That screws with the air velocity and flow properties. Just don't do it.
There should be other areas you can play with. I am not that familiar with the 4.6 head specifically, but common areas to get ported are the valve bowl (get rid of any lips so you have a smooth shot at the valve), valve shrouding in the combustion chamber, valve guides if they protrude into the port, ect. Head porting is really an art, and if you don't know what you are doing it is very easy to hurt low lift flow (where the valve spends most of it's time), resulting in lack luster performance. Do some research to see what those with experience on the 4.6 head are doing and where they take out material. I haven't done much searching, but my experience with the 4.6 has been that those who port like to keep the tricks of the trade to themselves (and reasonably so). Maybe that has changes now that the engines are getting older and more common.