496 can make 500 hp with fouled plugs...LOL.. I suggest getting some 320 cc aftermarket aluminum heads, prices are very affordable. My bud just had a 461 bb built with 10.25.1 cr, .575 lift hyd, Pro Comp 320 sq port heads, RPM intake topped with a 750 Holley. His engine will not be dynoed but engine builder told him a almost identical build made 579 hp and 550+ tq on their dyno. If you haven't purchased and parts look into getting a rotating assembley,..save a little $$