 A$105,000.Callaway received production-line 5.7L engines from GM's engine plant and replaced the original equipment cylinder heads, camshaft and valvetrain components with Callaway-designed parts, then shipped the engines back to Michigan where they were exported to HSV-Australia as Chevrolet RPO C4B engines.They were conservatively tuned and badged as with a T56 six-speed manual transmission and four-piston caliper disc brakes all-round; they were the flagship of Holden Special Vehicles.