northiam, I doubt idle vacuum would be that high.
clevoxt, If you want to see what is best and you've got time and tools to play around then try both.
Get your timing right, idle mixtures right, and run your engine up to oper temp. auto or manual?
Put a vacuum gauge on the engine and read the idle vacuum.
record reading and fit power valves up to around 2 inches lower than reading.
fit air/fuel ratio meter to engine, monitor all readings throughout rpm range under different load situations and jet, adjust carb, timing, etc to suit.
I usually try and get a/f to around the 13.2 mark under power.
Or spend around $120 and take to a dyno shop