For 1966, the GT 350 lost its Mustang tag and was marketed simply as the Shelby GT 350. The new model year also saw the introduction of non-white colors, including blue, red, green, and black. Other changes included special rear quarter-panel windows replacing the factory extractor vents, functional brake scoops on each side, and optional SelectShift 3-speed automatic, as well as an optional Paxton supercharger. The battery was no longer relocated to the trunk for 1966, and the over-rider traction bars were discontinued. The normal factory fold-down rear seat was optional. While early 1965 cars had black engine blocks, 1966 and later cars had their engines painted the regular factory Ford dark blue. The 1966 models came with a dual-exhaust exiting in the rear.
The first 252 GT 350s for 1966 began as 1965 Mustang K-Code Fastbacks. These cars were specifically ordered by Shelby American for conversion into 1966 GT 350s. Upon delivery to Shelby-American, the cars were randomly picked for conversion. The Shelby VINs do not correspond in numerical order with Ford VINs. The Ford VINs were shipped in 'blocks,' but many differ significantly because the order they were taken for conversions.
Source: Wikipedia (original)