Never ran a 216 but I would say unleaded regular is not a problem. If it pings then the timing is probably not right or too much buildup on the pistons causing hot spots. Doubt there could be enough build up to raise compressen that much. Valve wear with unleaded isn't much of a problem unless you really press an engine. However, when it comes time to do head work definitely go the hard seat route. Someone else might comment on what valve guides are available when redoing the head on one of these.
Dennis

40 Chevy 1/2 ton