point not only was it required with the 4-speed manual transmission, it also required the WS6 Special Handling Package as mandatory equipment. The W72 was only available for a very short time, with the majority of 1979 model year W72 Firebirds ordered in late 1978. By early 1979, orders for the W72 package were being rejected by dealers as they supply had run dry. Instead, they were substituted with the L80 Oldsmobile 403, or the L37 Pontiac 301 if they still requested a 4-speed transmission. On the invoicing for the 1979 model year Firebirds, they had the option listed as L78, however, every 1979 400 equipped car received a W72 engine. According to the June 2019 issue of Muscle car Review magazine, during dyno testing performed during that era, the National Hot Rod Association (NHRA) rated this Pontiac W72 400 T/A 6.6 engine at 260 to 280 net horsepower instead of the 220-hp rating published by Pontiac. The 1979 W72/WS6 equipped Trans Am was considered to be one of the overall best performing cars of the decade due to having a powerplant that produced more power than any other competitor on the market at the time with handling equipment to supplement the performance. 421 HO First offered as an option in 1963, the 421 HO came in a 4-barrel engine of and one Tri-Power H-O version with a hotter cam and efficient iron exhaust manifolds and rated at . Pontiac offered this to the public as a streetable version of the 421 SD. The engine came with 543797 (4-barrel) and 9770716 heads for the tri-power and special exhaust manifolds and a 7H cam with 292deg. intake duration and later 1964 L with 288deg intake essentially the same as the 068 cam. #9770716 aka "716" heads featured a 170cc intake port volume, and were considered a milder "street" version of the vaunted SD421 Super Duty heads. These same heads were also used on the 1964 GTO 389 tri-power engines. By 1965 and 1966 the same combinations would be rated at for the 4bbl and the two Tri-Power versions would be rated at and the H-O version at . 428 HO This engine was first offered in 1967 as the top engine option in full-size Pontiacs. It was rated at 376 bhp in 1967 and 390 bhp in 1968 and 1969. For 1967 only Pontiac called this engine the Quadra-Power 428. It