If you will meet the 330 days by October 15th, you can just file a regular extension.
However, I suggest you prepare your tax return now to see if you owe any money, because that is due by April 15th. You may need to set up some 'mock' dates in the program to exclude the foreign income.
You DO need to enter the excluded income in order to figure out what you owe because even though the foreign income is "excluded", it still DOES affect how your US income is taxed (in most cases your US income will be put into higher tax brackets).
