aluminium head questions

I've got a 505" RB with a factory sixpac with some tweaks running around here. He has a factory shaker hood and wanted the car to stay externally "factory". It makes around 550hp, just shy of 600tq with cleaned up RPMs and a solid flat tappet. With a 4sp it's a torque monster to drive and will spin the tires in 3rd at 55mph with 3.54s if you nail it. That intake was only gasket matched and the carbs use the ProMax jet plates. Otherwise it's just a well tuned factory six pac. If you get Stealths, be careful on gasket choice (use Source's and factor in it's thickness when designing the engine), and assume the springs, retainers, and locks will be tossed. Modern Cylinder Head (in MI) has a good program for them and Jeff does outstanding work for fair price.