Read too many horror stories with this setup, if check valve is between regulator and fuel rail, can cause overpressure and blow the gas line, potential fire in engine compartment, must be between source (tank) and regulator, since mine is "in tank", not an option.
Looking for two answers, main one now is why the pump doesn't prime at key on, verified with pressure gauge, nothing happens with key on, but once started 39 psi ...