A 737 type is a 737 type...in this case go with the cheapest. Start filling out the apps now. It's an in-depth and time consuming process, and just when you think that they are good to go, you'll see something that needs to be changed. Three months prior is WAY too late...the more time the better. Eventually you'll get to the point where all you'll have to do is update them periodically so that they are current. Good luck!!