yeah we need more informatino to know what exactly you're asking about. Otherwise we can't even come close to offering any usable info.
Except like..... 98V6 K.I.T.T. said...... "forged internals don't give you any extra horsepower, the parts are just stronger to hold up to higher horsepower applications."
I guess though, your rods and pistons can change your compression thus altering the way power is made through your engine, but you don't use forged internals to just increase power initially, just so you can run more more power or boost without busting up your internals.
You want to raise the compression for better N/A power (ie 11:1) or Nitrous and lower compression to allow more boost (ie 8:1), etc.
Edit: Perhaps you're thinking of a stroker kit, which in most cases you can option for forged pistons, rods, crank, etc. The idea really to getting these pieces put in is the ability to throw more at your engine before something breaks.
ok like was said your post is too vague. forging is done for the strength and durability not to increase power. it can help a little but not much to increase power over stock if the compression is raised. assuming everything on the stock motor is put onto the forged short block. if your car runs good and has been maintained i would leave the lower end alone and invest in cams, ported heads and all the bolt ons possible. you didnt specify if you have a pi or non pi 4.6. that alone can make a big difference.
If you are going the supercharger route then definitely forge your internals and go with a lower compression ratio. This will lower your hp before you put the supercharger on, but it will allow you to dial up the boost which in turn increases your hp.
So if you look at it that way, yes, forging your internals will increase your hp output in the end.