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What kit ? Usually, depending on the kit, a .047 Nitrous and .025 Fuel will get you there. I would give a quick call to your kit manufacturer just to be safe.
For the GTO? Those are the average recommended sizes for a safe tune on an LS1/2/6 with at least 50psi of fuel pressure. Some people also run stock timing but you may want to consider taking out 2 degrees for the nitrous.