[LMH]

The paperwork shows ownership and chassis number. Your state will assign a year to it when you register. In AZ, it is titled as a 65 but each state does it differently.

I am in the process of switching my car to IRS. It wasn't in production when I bought my kit but luckily, it can be bolted into the chassis. Is it worth it... IMO yes but it's kind of a matter of what your intentions are with the car and what's important to you. The solid axle can be smooth riding if you use softer springs. Kind of depends on how you want to set it up but all things being equal, the IRS car probably rides a little smoother and handles a little better.
Personally, I like IRS and would opt for it if buying new but I can't give any first hand experience with it in a Hurricane as mine isn't far enough along for feedback.
Larry