This latest FlyDubai. A6-FDY, was delivered on 13th and left Seattle at 02:40 on 18th. Normally they depart earlier and arrive GLA very early (arriving about 06-07:00) but in this case it was good. So that’s, say, 4 or 5 days from being handed over until doing the delivery flight.

http://boeing-test-flights.blogspot.com/ seems to be a good site to keep up to date with Boeing happenings like test flights, hand overs and stuff. It’s a good start.

Use that along with actual delivery flight dates to get an idea of average time between events. If you struggle trying to find delivery flight dates then have a look for FDBs at GLA on airliners.net or somewhere.