The correction of geometry, decrease in wear, improvement in alignment- those are all great reasons to bush the lifter bores, but the biggest reason I have is for the oil control. Try priming a BBM or Hemi with the intake off it and watch the GALLONS of oil that push by the lifter bores. We frequently run only standard oil pumps in bushed motors, no HV needed, and we also frequently need to REDUCE the oil pressure in those same motors after controlling the massive leaks from the lifter bores.