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Would there be any heads that wouldn't need the pistons machined???

You would need to contact the piston mfg and ask them if the dome you have will work with a Trick Flow head. You should be prepared to tell them about the cam you are using at the same time. The odds are that those pistons will work with your heads and cam but it might be tight. You will want to spend some time mocking everything up well before final assembly.