I had a 289 motor that was left over from my vintage road racing days. It's no slug, but wasn't competitive in this racing venue if you want to run near the front. That takes 450+ HP, and this motor is less, I'm guessing about 325 real HP, but I haven't dynoed it. It was originally in a race car that I bought freshly rebuilt by a professional race shop in Colorado. However, on my first day on the track, after about half a dozen laps, it blew up. It turned out that there was a mismatch in castings on the front of the motor that allowed the oil to escape. It makes me wonder about how many Ford motors that race shop had built. Anyway, I ended up replacing the block with a new 302 block from Summit racing, had the Carrillo rods refurbished (and one replaced), and rebuilt it with TRW 11:1 pistons, MSD distributor, the original ported 289 heads, Comp Cams solid-lifter roller cam (2200-6500 RPM, rough idle), roller-tip rockers, and the original Cobra high-rise intake manifold with Holley 750 CFM 4150 double-pumper carb. While maybe not highly competitive in serious racing venues, it's a plenty fast street motor.
Looked like this:
Note: eventually I ended up replacing this motor with the Weber-carbureted one shown elsewhere, but this is what this 289 motor looked like when running in the Z...