A air flow meter is about the only way to sycronize them things correctly, do the simple stuff first though, level the floats, screw in idle screws then back out 3 full turns as a starting point, jet both carbs the same, etc etc, then once you crank it up, (linkage undone) set the carbs to get the same airflow across both at idle, then adjust linkage out to have zero slack between the 2 carbs.
600cfms are kinda big for a little 302 - 450's would probably work better.
You might just run over that stock bottom end once you get it running.
Goodluck, Cp