heard em before sunrise, I'd go with spit. The gobbling is how I knew where they were roosting in a new spot I had not been to, and they started flying down right as the sun came up.
Personally I'd be exactly where I wanted to listen at 0600hrs CDT. That will give you a little insurance in case something happened unexpectedly and it would ensure you catch any and all gobbles, with most coming from 0615-0715hrs. My .02