The impending formal adoption of SAE J1939-91C creates an urgent need for rigorous, repeatable validation methods that extend beyond functional conformance. This paper presents a structured validation and benchmarking framework, with a focus on performance characterization across dynamic vehicle configurations. Building on prior work in secure network formation, rekeying, and Golden Tester concepts, we define a minimal, transport-agnostic set of cryptographic and protocol test vectors for deterministic validation of secure message authentication, alongside simulation-based methods for evaluating network formation and rekey behavior. The framework integrates performance metrics such as secure message latency, rekey time and throughput, while also introducing cybersecurity-specific diagnostics and logging requirements for gateway module implementation. Security validation scenarios are mapped to explicit detection and response benchmarks. The resulting methodology provides OEMs, Tier-1 suppliers, and research organizations with a practical, reproducible approach to validating J1939-91C implementations, supporting both development-phase evaluation and ongoing lifecycle assurance.