Change to 4-fold carburetor for oldtimer insurance?

Hello, now finally hit and bought a 69 galaxy 500 LTD convertible. The topic insurance is not difficult in principle, the only point is that in 2011 a noblebrock 4x carburettor was retrofitted. Was a 2-fold with the original 429 engine, now basically upgraded to a Thunderjet engine. In the letter / note nothing is entered, although executed by specialist company. The insurance now asks for originality, or counts this now as tuned? Must one specify something like this, can I’m sure no one can find out about that later on? With a traffic control no one can find out…. Thank you for your experiences! Greetings Gunter P.S.: Looking forward to picking up the car tomorrow like a little child 🙂