Those heads say up to .480" lift but I asked if I can go to .484" on mine and they said yes, you can go higher. I had plenty of spring left before it would bind so, I left it there and am happy with it. I'm not real happy with their lifters though
FYI - I just read their Q&A on these heads and saw where Summit Racing said they were going to change the maximum lift to .520". Their "Overview" tab now reflects that. Keep in mind these springs won't work well at 6,000+ RPM, the valves will start floating.