If it's not original, it might as well be wicked fast

 A lot of us have musclecars that may be very nice, but don't have the original numbers-matching engine. Unless your a concours show enthusiast restoring a car to the nth degree, I wouldn't mess with trying to chase one down. Even if your car isn't something ultra-rare-i.e. a Boss 302, SD-455 T/A, Hemi Cuda, etc, finding an original engine can be a virtually impossible task. If you have say, a 66 GTO-where are you going to find a 389 Pontiac with late 1965 or early 1966 date codes?  Or a 1963 327 to put in your Impala SS? Certainly not in your local junkyard.  Even later stuff is getting hard to find. Where are you going to find a 1972 340 to put in your Duster or Challenger? If you do, the seller is going to know what he has and it's going to be very expensive even for a rusted, locked up one that's going to need a complete rebuild. Since the engine you have or practically any one you buy isn't going to be numbers-matching, you might as well have one with awesome, greater than stock performance. Can't find a 340 for that Duster, Demon or Cuda? How about a Mopar performance 360 crate motor with 380 hp? Can't find a 440 for your Road Runner? MP has 500 hp, 505 inch strokers based on a 440 wedge. No 396 for that SS Chevelle? GMPP has rat motors from 454 to 572 cubes, with horsepower ratings from 425 to 720! No 327 or 350 for your Nova SS? How about a 383 stroker from GMPP or Blueprint engines? Can't find a hi-po 289 for your Mustang? How about a 347 stroker from Ford Racing?  You have a 68 GTO and a 400 block out of a 76 Gran Prix? Put a stroker crank in it and make it a 455. Add some Edelbrock or Kauffman aluminum heads, and your rockin'. Can't find a 330 for your 64 442? I bet you could find a 403. Besides being used in hundreds of thousands of California and high-altitude Pontiac Firebirds and Trans-Ams from 77-79, they were also used in thousands of Buick,Olds and Pontiac station wagons, Electras,Rivieras, Bonnevilles, and Catalinas. Besides the 73 extra cubes, you could add Edelbrock heads, cam and intake and have way more grunt than even the revered and rare "W-31" 350 Olds engines. Since it's not original, who cares if it's modified? And you can race it, and not live in fear of throwing a rod out the side of a numbers-matching block. I'd sure do that rather than searching the galaxy for an overpriced core with a certain date stamped on it!  Mastermind