The headers are "180 degree", the cylinders that are at TDC at the same time are paired with equal length primaries.
That's why they appear symmetrical - even looking a little gay, if they were built down from the ports as the headers make their way to the rear, I couldn't get the equal length primaries, hence building them upwards first.
The Y junctions have a divider to keep the gas velocity up by reducing the cavity of the junction to produce the maximum negative pulse in the other runner.
180 degrees later the other cylinder returns the favor
![Smile :) :)](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f642.png)
The design is to maximise scavenging.
Hard to do on V8s because you have to pair cylinders on opposite banks such as done on the Ford GT40.
These outlets are high, "downpipes" will connect the cats at about 45deg as they appear on the stock manifolds.