As someone who’s worked hands-on with Boss 429 engines, I can confirm they genuinely live up to the hype—but there are a few things you need to know before you buy. First, authenticity matters: real Boss 429s (casting codes C9AE-E or D0AE-E) are rare, and block stampings like 820-S or 820-T instantly impact value. Don’t confuse these with aftermarket Ford 385-series big blocks; the Boss 429’s distinct heads (casting numbers C9AE-6090-S or D0AE-6090-T) and dry-deck setup set it apart. When purchasing, inspect for proper oil restriction in the head and check the factory magnesium valve covers for pitting or cracks—they’re often swapped with cast aluminum replicas. For a period-correct restoration, always source original brackets, pulleys, and the specific spread-bore Holley 4-barrel carburetor. Rebuilding? Use ARP main cap and head bolts whenever possible, and replace the original timing components with modern, billet versions for reliability. Boss 429s were temperamental if oiling wasn’t spot-on; I always recommend adding a high-volume oil pump and ensuring the oil passages in the dry-deck heads are clear. If performance is your goal, adding a roller cam and modern valve springs can unlock well over 600 horsepower—but for purists, even a stock build is impressive. Honestly, nothing compares to dropping the hood on a finished Boss 429 Mustang and hearing that first start. Having installed and tuned several, I’ll say they’re not a budget-friendly build, but every minute is worth it for the end result. Whether you’re restoring a ’69 Mustang or building a vintage race car, the Boss 429 engine stands as the ultimate Ford V8 statement.