Why the 318 is a phenomenal engine...

I bought my Dad's '71 Satellite when I was a teenager. The 318 ran fine, but I wanted more go of course. Here are the changes I made at 110k miles.
Freshened the stock heads. Nothing special
Double roller timing chain/gears
Dual exhaust (2-1/4")
Direct Connection purple shaft
1970 Factory 340 intake manifold
Holley 4bbl (600 cfm?, I don't remember)
Lightweight spring on centrifugal advance

It ran great and (miraculously) nothing ever broke!

Note: The transmission had already been rebuilt before the above changes; and then I did the B&M Trick Shift kit myself after the above mods.