NO, YB, they are not optional on hydraulic flat tappet lifters, only the solid lifter flat tappet lifters. it can't be done with hydarulic lifters, it would bleed off the oil pressure and every lifter would be clattering due to like of pressure. I'm pretty up to date with Crower and in fact just ordered a set of fuel injection nozzles today from Jerry, who still makes them at home, since Crower no longer is in the injection business, thay sold all their injection parts and stock to Rons injection.
Zip.