Firstly, the stock rockers are 1.73 ratio, so no one would be using 1.5 or 1.6 on these motors, unless they had a cam re-grind to compensate.
I once pondered the idea of putting 1.73 on all the intake valves, and adding 1.8 rockers to all the exhaust. Keeping in mind I already have roller rockers, which do not come stock.
It would take an engine builder or someone with equivilant knowledge to answer if this is possible.