Registration to have an N number must have been started before 1/31/2008.
Once you have your formal N number from the FAA on the 8050-3 "hard card", you need to talk with the DAR and send the following:
1) A copy of the 8050-3 Hard Card (Note: This is absolutely critical and all following forms MUST match the Hard Card exactly!)
2) Form 8130-6 filled out. This is an Airworthiness Application. It MUST match the Hard Card exactly!
If you are not applying for an Operating Aircraft Experimental Light-Sport Aircraft(ELSA) such as Amateur Built Experimental, Special Light-Sport Aircraft or Kit Built ELSA, then use see those sections for detail differences from ELSA Operating Fleet.
3) A program letter. See sample
4) Pictures or drawings of the plane
5) Weight and balance calculations (Weight and Loading for PPCs and WSCs) for "empty weight", "Forward CG loading", "Aft CG loading", "flight test planned CG" and the manufacturers CG limits for the design.
Make sure you include a complete list of installed equipment.
For Powered Parachutes and Trikes you may use the weight and loading data that is provided by the manufacturer.
6) You must have a verified number for the Exemption 6080H that allows this late inspection.
7) Marking the plane
Here is a sample of a powered parachute marking http://www.sportpilot.info/sp/Marking3.htm
Here is a sample of a fixed wing marking http://www.sportpilot.info/sp/FW/Marking4.htm
Thanks to Bill Czygan for providing the help on marking.