The old heads made 33bhp improvement over stock heads. The new heads make 30bhp more than the old heads. AFR's New Eliminator 23 Degree SBC Head Raising the Bar in Performance Yet Again Whopping 10% increase in flow at all valve lifts.

Light weight 8mm valves, valve springs, retainer and lock components Light weight parts reduce valve float, increase reliability and performance gains of 75 HP with hydraulic roller cams at 6500 RPM The RACE 195cc Flows 300 CFM at .550 lift The Street 195cc Head Flows 280 CFM @ .550" The Awesome 210cc flows 310 CFM at .600 lift!! Most efficient, highest flowing 23 degree head available street head out flows our competitions race head. No other true bolt on 23 degree head comes close!! ORDER NOW - LINES ARE LONG PERFORMANCE IS UNEQUALLED      SuperFlow Dyno BHP numbers. For SAE BHP numbers multiple by 94.5 535-SF/BHP becomes 505-SAE/BHP  See More Explianation Here

The above test used a Hydraulic Roller Cam 236/242 @ .050 and a RPM Airgap Manifold

The test below used two flat tappet hydraulic cams, the RPM Airgap Manifold and a Victor Jr.

The results reveal stepping up to the Victor Jr manifold made 17bhp more but lost 15ft/lbs torque, this is seen on most similar type tests.

The cam change of 10 degrees more duration @ .050 made 30bhp (518bhp) more,
torque was down 20ft/lbs @ 3000rpm and recover at 5000rpm 

Using this data we can expect the motor above making 530bhp to achieve  560bhp plus with a Victor Jr and 240 In. dur. @.050 cam.

Another option to hang on to torque but make the bigger BHP numbers is an EXTRUDE HONED RPM Manifold, expect to pay $650 for one of these manifolds.

These heads come in two chamber sizes.

Using a .040" thick head gasket and zero piston deck height we get the following...