After being told that it would cost $300 in machine work and parts to run stock Vortecs with my roller cam (.452 max lift), I was to the point of selling them. I feel bad, I did offer them for sale at one point, I really thought it was worth it to just get ones already done for more lift. However, on a tip, I called the machine shop that had done another set of heads for me a few years back. Lets just say, that Z-28 springs, with the inner damper removed, have 112# of pressure installed, only *2*lbs over what Crane recommends. To honor what the shop asked of me, I can't give the exact cost, but it was WAY (way way way) under $300...well worth it compared to going with the "complete" already prepped Z-28/Vortec heads. /forums/images/graemlins/smile.gif The cost included a check of the seat pressure obviously, but also checking maximum lift 'till coil bind (.572") and checking at what lift retainer to seal interference would occur. (.550") As always, it's good to deal with people that know what they are doing! Hopefully anyone considering these heads can use this info to get an approximate idea of what they will be dealing with.