Is it a 4-bolt main with forged crank? That will have some effect on your rpm. Have the rods rebuilt and add ARP rod bolts. Add a good oil pump.
Stock 454 Mag bottom end, 6000 rpm for a season
http://www.justanothertoy.com/photog...dup/42mphe.jpg
Note evidence of a "little" heat around the saddles!
http://www.justanothertoy.com/photog...dup/42mphg.jpg