Mike,
Register it using SB100. It's not that big of a hassle and it saves you from a potentially huge hassle on down the road if the DMV ever catches that you have improperly registered it as a 1965 Cobra. Falsely titling a cobra as a 1965 is what people used to do before SB100 was passed and a lot of people got caught. They used a company called Titles Unlimited who would "buy" your car from you, title it as a 1965 in Alabama or somewhere and then "sell" it back to you so you could title it as a 1965 in California. California found out about it and shut it down and made it clear that it is illegal to title a replica car manufactured in the 2000's as a 1965 model year. The California Deputy Attorney General used to come post on Club Cobra about the title registration problem. Do a search. He posted under the name "Morgester." His posts were candid and informative. Here's a thread about the Titles Unlimited debacle:
Titles Unlimited Also talk to Randy Rosenberg. I think his was originally titled using Titles Unlimited and he had to switch to SB100. He could tell you what he had to go through.
Chris