Maybe look into a set of CJ exaust manifolds for a little more flow then if the original look is wanted. They are getting expensive though. As for the crank your 390 nodular iron crank can take 600-700 hp. Your stock rods will be fine and you can upgrade them with a nice set of ARP bolts and nuts. Following the "correct" theme maybe look inot a Blue Thunder PI repop intake. It will like that 725 a little better. Looks like the original 428 PI aluminum intake and flows better than the Edel RPM. JMO, G.