It's the Camper Special head developed for Jake Raby's engine program. The combo of those heads with a specific cam has (from what I read) a significant power upgrade. I put my current engine on a dyno a few years back and I make 55 horsepower at the wheels, which is pretty typical. A bus is a surprisingly heavy, non-aerodynamic vehicle, designed for American highways with a 55 mph national speed limit, under very tight emission standards, with a low purchase price being the number one factor in its design. If you've ever driven one, you'll know what 55 horsepower feels like on highway hills.

Additionally, everything I've read says the AMC heads (which are the new castings, as VW does not make them anymore) have junk hardware, and the valve seats fall out, which is a common problem with the VW bus. I've dropped two valve seats over the years in my bus, and it sucks.