I run 906 heads on my 63 that I ported and added the 2.14 and 1.81 valves. I dont know what the flow #'s are as I never checked them. I just put them on the car and used them. I can tell you in my mild 440 I dont think stepping up to the 2.14 and 1.81 valves helped much if any. But I did it in case I use these later on a stronger engine. I cut mine .060 and the heads cc'd at 76. As for the cost of installing the larger valves I dont know as I did mine myself with my brothers valve grinding tools. I do all my own work so it dont cost me much to work my heads but if I had to pay for all the work I would buy the Stealth or Eddy's for the money. Ron