If I were where you are now, with those rocker parts already on hand, I'd just call Smith brothers and order up some adjustable pushrods.
Set the preload where you want it, and forget about it.
This is what I did on the last 2 builds I did for others, cost for the pushrods was about $225 , I had a couple of extras made as spares.
It's a lot easier, and less time consuming, than swapping rockers around THINKING you are going to magically find .050 preload difference. That only happens if you are certain valve stem heights are the same from valve to valve.
