If you are getting valve train noise with low oil pressure-----you may have lifters that has the oil groove band coming out of the lifter bore , too loose a fit of lifters to tappet bore, oil restrictors somewhere, wrong matching (mismatched) pushrod to rocker or tappet radius---

in other words---if you get noise when oil pressure is low---you got to fix cause of low oil pressure----the lifters will still see the exact same pressure no matter what the pushrod length is