Could I ask that you reach out to Murata to discuss an equivalent antenna which leverages their existing certification via a Class 2 permissive change? If you must negate their certs completely with an entirely new antenna design, we would have to refer you to a Engineering Services partner that could assist with the re-certification process as that's not something we support within the broad market or on the community.
Murata doesn't support that kind of special request for broad market. Please contact your local Murata person to get further assistance. There are several way to pass FCC.