Is there different heads that came with 440 six pack are a 440 with a 4 barrel on it . Would it have bigger valves on the six pack over the 4 barrel ? And how would u tell the difference between the two . One would think that the six pack would have bigger valves than the 4 barrel. R there numbers on the heads to tell them apart? And some one had gave me a gift and I wanted to thank them .