I have a rebuilt and balanced 221 which we have put a classic inlines head on the motor has a 570 holley ,xe electronic ignition rebuilt for the 221 by performance ignition ,YT roller rockers , 280/280 cam , pacemaker headers it went on a dyno to get the ignition and carby rite at the end of tuning they gave it a quick run up to 5000 rpm and it put out 150hp with a bit more tuning when the motor is run in i was hopeing for around 200hp but im thinking it mite be 170+