Six-packs are cool, but it's mainly eye candy when you pop the hood. Doesn't really add much more performance (if any) than a good four-barrel that's tuned. Kinda spendy for eye candy.
I'd put mods into wheels/tires, which can totally transform the car. Then maybe then suspension (get some really good shocks) and disc brakes (both F&R if you already have fronts).
BTW...big block or small block? automatic?
More pics?