I wish I could tell you that there is an easy way to figure this out, but there is not. Different manufacturers bases vary in height by as much as 3/8", some ring manufacturers give you dimensions from base to bottom of scope, some from base to center line of scope.
If you order High or Extra High, you could end up with the scope WAY above the barrel, which will cause a cheek weld problem and significantly reduce your ability to shoot the rifle accurately.
You really need to have the base in place on the rifle, and then block up the scope to get an accurate measurement of what ring height you need.
Dave