Hi Buddies, happy new year...
My KHK runs with std HD K springs, the very ones that were in there when I bought it in 1987 and I've had it quite high in the revs while changing gears...
Never hit a valve or a piston or broke anything in the valve department over the years!!!!
Seriouly, got one day a set of "race" single springs for K or KH... Guess what, they went coil bind before KHK cam full lift... What a waste of time!!!
Unless you strobe your cams like Tom Sifton did in the old days at 3000/3500rpm to see your springs real action and correct the defects/vices of specific cam individually, pretty much any springs of the right poundage will do...
Patrick