Went to see a 68 Barracuda notchback black on black

Get it because you like it. Don't get it for investment unless you do a lot more checking into the market. The market in the states, the market in the UK, and the market in your area of EU are all going to be a bit different.
That car has been through a lot of alterations. In the US, I'd say 2-3K minimum on just the body to make metal, trim and glass reasonable decent. Then there is interior and a fair amount of time sorting out the mechanical and electrical. Swaps, or returning to truly original will be even more time and money. My opinion is that modified cars should be done because that's what the owner wants. The market for your creation will generally be smaller than a restored car.