These are ported 305 heads. They are disassembled and come with Z-28 high rev springs, retainers and Comp Cams roller tip Magnum rocker arms, fulcrum ***** and nuts. All you need are valves and seals and you're ready to go. The intake valve size was increased from the stock 1.84" stock 305 valve to a 1.94". I have flow numbers and casting numbers. Email me if intereseted at Cory0550@yahoo.com