Asp,
Here's an older dyno run on a 429
If you look at the top of the message you'll see a comment about the output of the 521.
Link:
http://www.460ford.com/viewtopic.php...ight=boss+dyno
Either appears adequate for a street engine, which is what Kaase seems to be mostly interested in.
The 521 is in the 900hp area, the 429 produces well over 750hp.
Nice!
Tom