There is a lot of info out there and a lot of bad info. Basically, if you want to buy a new W head the 9 and the 2 are still available. W8 is regarded as the best of all the W series with a thicker deck than the others among other things. But you will have to pay big bucks to get a set of 8's. Pretty much all of the W heads are meant to be ported for them to work except the W2. All of the W series use an offset intake rocker so the port opening can be bigger. All of the W series uses their own unique intake and exhaust. So if you invest in W2's (which are a great head by the way) with W2 intake, rockers, headers and you decide I want to move up to W9's you will need to buy all that stuff all over again. The cool thing about W heads is that they are factory designed which means the combustion chambers are light years better than any of the Edelbrock, Speedmaster, Pro Comp, whatever cheap head out there. W7,8,9 are 48 degree heads and can't be put on a 59 degree block (without being modified anyways). Also W8 and 9 have extra head bolts which are great for power adder motors looking for big power.