If all the numbers are issued for 2009, you will have to wait until the first business day of 2010 for a 2010 SPCNS number. Be sure and bring all the DMV forms and your check book. If the car is drivable when you get the sequence number, ask for a 30 day Temp Operating Permit so you can complete registration process process. If it's not drivable, don't accept a TOP, Some DMV's wil only give you one 30 day TOP. If your build is going to take more than a year to complete, for your second year, you can register it as non op, and get a break on the registration fees. This only applies after the initial registration has been started. I talked to a CHP officer about this, and he said it was perfectly legal.
I have a booklet somewhere that explains the whole SPCNS process. It was culled from info available on the 'net and if I can find it, I'll post it here. John