The 166 is basically an evolution of the 164, but I'm not a fan of the rounded look.
I assume his 166 was an interference engine design where the valves will be struck by the pistons if the timing fails.
He probably had to replace most of the valve-train.
I've watched a mechanic make a mistake trying to fix an interference engine, and bend all of it.

Today cars are all kind of similar because there are so many regulations, and most can't really try to do something different.
The Tesla Cyber Truck is an example of doing things different, but I don't understand how they managed to get around so many regulations.