Found nothing but the ST220's. Anyone else ever find/ use anything else? Don't know how the valve train would hold up with too much extra force on the springs but off the top of my head I figured 10-20% over stock wouldn't be a problem- like somewhere between 170-180? Anyway, the head shop said he could measure the springs and probably find a replacement in that range that would work. Probably not necessary but I feel a bit more 'comfort level' with someone like Isky, Crane, Crower (or Manley) and a spring force a bit over the 160- then again, my intent is to never EVER go over 7500 and over 6 should be rare (well ocassionally). Machine shop said their equipment is only good to 8K anyway.