I'd be interested to know what the port size is on that manifold.
View attachment 1716195147
Since it has the 273-only throttle cable bracket boss (red circle), and the early 13/16 bypass fitting (green circle) makes me wonder if it was also engineered with the smaller 273 ports in mind... hard to tell in the pictures, but it does appear to have the later intake bolt size and angle.
Just curious- no personal experience with this particular manifold.
