The 1963 Grand Prix 421 HO.
Although not quite the beast like the 421 Super Duty - a hardcore 11.0 and 12.0:1 compression race engine- the 421 HO was a more suitable mill for street driving, boasting Tri-Power and 10.75:1 compression. The engine was much more streetable, and still churned out a massive 370 hp and over 460 lb-ft of torque.
I think there were 267 Built
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