408 cam / build help.

With just kinda starting out and I assume somewhat limited resources, I would build the bottom end and use your current heads. As long as they are mechanically sound. It is easier to upgrade the top of the motor as you go along. A cast scat crank is good for about 500 hp, if the end goal is higher go forged. Stay away from eagle cast cranks. I would take the $750 and save it towards buying your final head choice. Which probably will be aluminum. The pursuit of more power is never ending.