3. 1968 Pontiac Firebird Sprint
Since 1968 was the height of the muscle car era, the public was focusing on high-powered V8 models. However, Pontiac managed to sneak an interesting model they named the Firebird Sprint. The secret of the Sprint was the 250 CID straight-six engine with a single overhead camshaft. It produced 215 HP during the 1967 to 68 model year, and 230 HP in 1969.
Compared to the 350 and 400 CID V8, this was not impressive. However, the six-cylinder Sprint had serious torque and low weight, so it revved happily to 6,000 rpm. In the days of V8 monsters, the six-cylinder Firebird had an almost European feel.
Unfortunately, not many people understood this model. Despite the modest price and unique characteristics, they only sold a few thousand in the three-year production run. Today, the Firebird Sprint is a rare sight in the six-cylinder muscle car category, which makes it highly desirable.