Figure I'll provided a bit of an update, and always open to suggestions and advice:
Registration / titling: I think I'm close with getting the car retitled as a 1965. It's been a lot of conversations / communications with forum members, one of the inspectors and the title department. All have been helpful. I'll leave out a lot of the details that got me to this point, but DMV agrees that the title can be corrected to 1965 Composite Cobra, and the registration updated as well.
However, they are saying that composite vehicles do not qualify for Classic plates. This concerns me, since the classic plate is what firmly caps the tax assessment at $500 (vs. the $50,000 they are currently [incorrectly] assessing it at). Without the classic plate, I think the assessors will continue to abuse me, even with a 1965 title. Also, my car is currently registered as a 2004, so would be 20 years old in 2024 (which should then be eligible for classic plates), so should I stick with it as 2004? If I go to a 1965 registration w/o the classic plates, not sure that that means for an assessment. I think they will still use their 'google search' and pick high value, non-representive replicas for the assessment.
Another forum member was titled in CT as a 1965 Cobra Roadster and got classic plates, but I'm told they won't title it like that for me.
Assessment: I appealed the 2020 assessment earlier this week.
TBD is approved or declined. I will say that at least this year, the 1-person panel member seems knowledgeable in these cars to an extend, and hopefully I made the case very clear on a 18 year old factory five kit vs. other high end kits. We'll see the result after he reviews it with the other panel members for a decision.
If these paths don't work, not sure what I'm going to do, but I cannot sustain an additional $5000 in vehicle property tax over the next 3 years (or longer!).