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The Super-Duty 421 engine cranked out 405 hp at 5,600 rpm and 425 lb-ft of torque at 4,400. This beast was machined by Nunzi Romano and assembled by the owner. Displacing 433 ci, it features No. 980 cylinder heads, a compression ratio near 13:1, a radical mechanical camshaft from Nunzi's, and a points-type distributor likely used by Pontiac engineering. Pontiac's '63 Engine Production Log shows that just 59 code-13 engines were built that year.