The beast locked in the 4.6

When my Dad was young he had a 1971 Ford Thunderbird that came with a 429 rated at 300hp stock. He had it rebuilt by a guy who makes Chevy Engines (go figure) and had it beefed up. When he got it back it was cranking around 600 HP naturally aspirated.

I was curious if one were to drop off a 4.6 at a shop and tell them a rebuild with beefier parts, what is the 4.6 Capable of without intake assist.

I mean, it's obviously a very moody engine (Typical woman). I've had days when my thunderbird is like "No, thanks" and other days when it's like "Let's find us a mustang". You can feel the power locked inside of it. But what is the extent of that power.

Depends, is the 4.6L a SOHC or DOHC?
Then it depends on what year SOHC or DOHC
due to the different cylinder head designs & different intake designs.