3.4L E-Vin Question

Hi, I have a valve noise on my 3.4L OHV motor, this uses the pedestal type rocker so there is no adjustment. I did recently put in Mobil 1 5-30 weight oil, should I replace this with a 5-50 or 10-50 Pennzoil or Castrol? The noise gets worse as the motor warms is actually quiet when cold. Another question, the 3.1L OHV is essentially the same motor, I have seen the older stud/ball/nut adjustable rocker on these, can I do a quick conversion by just replacing these parts? Is there machining involved? Thanks in advance.

Dan