Describe your lifter issue. Some are immediate ...as in until the pressure comes up and others linger. Mine would be silent upon cold start THEN start ticking. It would cycle until the oil got fluid enough. It didn't matter what visc I used, nor weather it was conventional or synthetic. I tried everything (Gunk, Seafoam, and MMO). None of them worked at my problem. Auto-Rx did it the first time. I'm uncertain if the other products would have worked with continued use.
You can use any weight oil you please in that engine. From 5w-20 to 20w-50. The variable will be shorter trip fuel economy. It's a great engine if you keep your cooling system up to snuff. Longer term cooling system neglect can result in external head gasket leakage.