The one big thing I've learned from this site about this engine is that it was crippled from the factory in an attempt to meet emission requirement. Changing out the cam and timing set help this quite a bit. As with all engines, good breathing is important, so intake and exhaust are worthwhile.

Check out the article that Dave wrote at
https://www.ford-trucks.com/article/...00_Engine.html
As a comparison, a 460 is a bigger motor, so it's possible to build it to have more power. But the 351M/400 engine has plenty of potential, and it's lighter.

Above all, have fun and build something you'll be proud of.