4-Door with 340 from the factory?

Jim Lusk, You are right the W2 head was on the drawing board for the 78 Little Red Truck and was nixed for smog. My guess is that the W2 head does not have the exhaust heat crossover. Which would have made the EGR valve on the intake manifold inoperable which was a part of the smog equipment for those years. Just my guess.