i.m not sure if i'm reading you right ,sorry if i missed your question.
1. stock rocker arm for gm/smb is 1.5
2 formula for finding out 1.5 to 1.6 difference is :e.g.(480-divided by 1.5 =320
3.480 divided by 1.5 is 320 then multiply by 1.6 (320 times 1.6=512 lift.
If you are interested,I have a brand new set of C.A.T. 1.6 roller tip rockers these are same as Comp Cams Magnums 1416-16 will take $85 shipping included.Also you might check the add I posted for a deal on springs&retainers.
It depends on where you need flow. Basically adding more rocker ratio is like adding just a tiny bit more cam. The faster ratio means the valve is at .050" lift sooner, so it simulates another degree or so of duration, and of course provides more lift.
The thing is, you have to determine if you NEED more lift. Find the flow specs for your head and match valve lift to where they flow. The reason many SBC builders choose the staggered ratios is because many SBC heads can use a little more help on the exhaust especially if you use an equal-pattern cam.
Adding too much lift can hurt power, or at least not improve it any more past a certain point.