i dont believe it will hurt to put 305 heads on however your compression ratio will increse witch means your want to caculate your new comp ratio for gas octane level.. as for pistons, you dont need to change then because they are not apart of the head... rather a part of the block and most likley you dont have dome pistons in a stock engine.... i would take it to a machinest and ask him for his advice and not take fourms help.. machinests advice is free so dont be woried to ask. ( if your not gunna go visit one then make sure the diameter of the head is the same size as the piston.