The T221 didn't start until '60. The Napco and Task Force/Blue Chip 4x4s used the Spicer 23 transfer case.
It might be worth noting that the GMC Napco and factory built 4x4s did have a V8 option with the same drivetrain components as the Chevrolet, plus the option of the Hydramatic with 4 wheel drive, which Chevrolet did not offer.
