For the most part a title that says the car is a "1965", and we know a replica is NOT, is little more than smoke and mirrors. It can cause more trouble and legal problems than it's worth. If someone says it's registered as a 1965-66 and "hypes" about how cool that is, just blow it off, it don't mean squat to the DMV. Unless, the DMV can figure out how to charge you with FRAUD, then it has meaning!
5 speed is not a "must have", sometimes it's nice to have, but a four speed works fine, in some ways BETTER than a 5 speed. I've had both, there are times I wish I still had the 4 speed, other times I like the 5 I now have. Hmmmm, it depends....
Of course the newer models (SPF, ERA, Backdraft, whatever) show improvements. Some are safety related and older cars have been up-graded, other "improvements" are not that significant. ERA has gone through some nice changes, but nothing extraordinary in my opinion. The early cars are very rock solid and worthy "as built" without up-grades. As far as SPF, I'm no expert. Some things that come to mind are paint issues and strength improvements here and there. I suspect the early ones are fine and the newer ones are better, typical of any car make.