That 505 had Edelbrock heads. The TF heads will make 600+ hp with pump gas compression. The 496 in my Coronet is 9.8 compression and it made more power than that high compression 505. The key is to use a flat top piston with tight quench and then put a dish in the piston to get the compression that you want. And you need the correct cam to match the heads. The 505 article was written 10 years ago and some things have changed since then.