The two fittings use entirely different sealing mechanisms. The original fitting is designed to seal using a soft copper gasket that crushes to create a pressure-tight connection. In contrast, the new brass fitting is an inverted flare type. This design relies on the precisely-machined flared end of the brake line seating perfectly against a matching flared surface inside the fitting to create its seal.
Because these designs are fundamentally incompatible, I have serious doubts that the new fitting would seal properly. A leak in a brake line would lead to a complete loss of hydraulic pressure and, consequently, a total failure of your brakes. Given that this is your only way to stop the vehicle, attempting to use this incorrect part would be extremely dangerous. I strongly advise against it.
