HP 440 RATEING ... How much power will i have ?

The aluminums have the same chamber size as your 915s. If your engine (or the one the heads came from) was a '67 HP engine, then they are 2.08/1.74. If the engine was a standard 440 (as in no HP stamped by the factory on the ID pad near the driver's side front of the valley area) then the heads came as 2.08/1.65 exh. Not all 915s are the 1.74 exh valve. Good heads, by the way. The problem is the pistons.