I really need some advice here

Stroking pretty much any engine adds anywhere from $1200-2500 to the build. There are at least dozens of folks on here running quick 360s. There's no specific "need" for a 408. Build the engine well, set up your light little Barracuda correctly, and you'll have little trouble keeping up with, or walking away from potential competitors...until you run out of gear. Pretty sure you can build up a 425-450 horse 360 capable of fun times...but I agree more with rumble...suspension and chassis are where the real improvements lie...having power isn't worth jack dammit if you can't put it to the ground.