??W2 Econo valves??

Ok guys. So rumblefish says there are one style econo w2 that can use either length valve, and aarcuda says there are TWO different versions of the econo w2 that require their own specific valve length. Who is right?? AARcuda- if you could, please check your heads and see what the difference is. I have a completely bare set of heads and don't know which valves it takes-you see my problem? I can't just take one out and measure it.