The days of junkyards bursting at the seams with rear-drive cars packing big V8s are long gone, but you can still go into most self-service yards and find a couple of big 80s Fords with complete 351 Windsors...
Of the 200 or so engines Ford decided to call a 351, the small-block 351 Windsor was the only one that was reasonably easy to swap into a car that started life with a 289 or 302. It's a bit wider and taller, and in keeping with Ford tradition it doesn't share many parts with its nominal small-block siblings, but the Fox Mustang guys know it fits in a Fox car's engine compartment with medium sweat application. Sure, it generally requires a hood scoop or cowl to clear the air cleaner... but hey, that's not a bug- it's a feature).
In addition to the complete 351W with all accessories- including the electronic ignition system- this LTD's got a 4-speed AOD transmission (and you can tell the car started life as a police vehicle by the "Certified Calibration" label on the speedo). I know a guy who put this engine/trans combo in a '65 Falcon wagon and the result was a sweet-driving car that has good power and decent mileage.
Don't forget the dog-dish hubcaps while you're grabbing parts! What car doesn't look good with dog-dishes?
Related:
Half-Price Day Junkyard Day [internal]