Help... Need 600hp or is it possible
Even with an "unlimited budget", you'll go broke before you're 75% done with an FE!!
The Windsor would be cheaper and there are better parts available from the aftermarket. A stroker kit with good aluminum heads will get you into the 600 HP zone in no time.
With the FE, you'll be paying outrageous prices for 35+ year old parts, then you'll need to fortify it with aftermarket parts too!