The blocks and heads are the same. The intakes are a little different though. The lowers went through some changes, mostly in the way the fuel rail mounts, and locations of sensors, etc. The upper intakes on the Gen 3 use a separate throttle body, whereas the Gen 1 and 2 cars have the TB incorporated into the upper intake.
The Gen 4 Vulcans have a composite plastic intake, along with the MAF. They also use a separate TB like the Gen 3. The theory is that the plastic does not act as a heat soak, resulting in a cooler intake charge.