In short, my cam is too small, want to upgrade. Willing to buy new springs and retainers as well.

I have '70 heads with stock guides and stock-length valves. Can't easily measure retainer to guide clearance unless I take stuff apart. I realize the best you guys can do for me with this question is a quick estimate, and that's fine.

Going to be racing against my brothers, so its a must-win situation...