30% HP increase on an otherwise stock engine? This is right up there with the slick-50 claims. Pure and simple advertising baloney. Notice they don't mention where in the RPM range the alleged increase is shown. And these are all high output multivalve examples - a 292 is stifled by the non-crossflow, siamesed head design that can't be improved without major work and expense. Headers provide a minimal increase on a truck engine designed for low and mid-range torque.
Cast headers cost more because they are more costly to produce and machine (they don't pop out of the molds ready to bolt on), but you absolutely get more for your money. Longer life, no rust-out, quieter operation, etc. etc.
The Fenton and Stovebolt cast headers are reasonably priced for a niche market product. If cheap is the only criteria, go for the tube headers, just be ready for some grief down the road.
